JP7337642B2 - X-ray CT device - Google Patents

Description

An embodiment of the present invention relates to an X-ray CT apparatus and an imaging planning apparatus.

2. Description of the Related Art In recent years, with the increasing definition of X-ray detectors, a sequential acquisition system DAS (Data Acquisition System) has come to be used in CT (Computed Tomography) scanning. A sequential acquisition DAS sequentially acquires X-ray signals detected by a plurality of detection elements while shifting the timing for each detection element. For example, in a sequential acquisition DAS, a plurality of elements share one A/D converter and sequentially perform A/D conversion. This allows one DAS to collect signals from a plurality of detection elements, thus reducing the number of DASs relative to the number of detection elements.

Also known is a technique of using X-rays of two different energies in a CT scan to perform dual-energy (DE) acquisition. Also known is a technique of multi-energy (ME) acquisition using X-rays of three or more different energies in a CT scan. This makes it possible to collect projection data corresponding to each energy and to discriminate the types, atomic numbers, densities, etc. of substances contained in the subject by utilizing the fact that X-ray absorption characteristics differ for each substance. be. DE acquisition or ME acquisition is performed, for example, by a high-speed switching method that changes the energy of X-rays for each irradiation angle of X-rays with respect to the subject. A fast switching scheme, for example, changes the energy of the x-rays for each one or more views. Here, when performing DE collection or ME collection by the high-speed switching method, a simultaneous collection DAS is normally used. A simultaneous collection DAS is provided for each detection element, and charges are read out at the same time charges are accumulated in the corresponding detection element.

JP 2014-61286 A JP 2014-45896 A WO2008/75595 JP 2012-200555 A Japanese Patent Application Laid-Open No. 2017-119002

The problem to be solved by the present invention is to enable dual energy collection or multi-energy collection by a high-speed switching method using a sequential collection DAS.

An X-ray CT apparatus according to an embodiment includes an X-ray generator, an X-ray detector, a collector, and a controller. The X-ray generator generates X-rays. The X-ray detection unit has first to n-th (n is an integer equal to or greater than 2) detection element groups that detect X-rays that have passed through a subject and accumulate charges generated by the detection. The collection unit collects detection data for each view by repeating a process of reading out charges accumulated in the first to n-th detection element groups in groups, starting with the first detection element group. . The control unit periodically changes the energy of the X-rays irradiated to the subject and adjusts the energy of the X-rays irradiated to the subject while acquiring detection data for one or a plurality of consecutive views. is substantially equal among the detection element groups.

FIG. 1 is a block diagram showing an example configuration of an X-ray CT apparatus 1 according to the first embodiment. FIG. 2 is a diagram for explaining control of X-ray energy according to the first embodiment. FIG. 3 is a diagram for explaining control of X-ray energy according to the first embodiment. FIG. 4 is a diagram for explaining control of X-ray energy according to the first embodiment. FIG. 5 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus according to the first embodiment. FIG. 6 is a diagram for explaining the simultaneous collection DAS according to the first embodiment. FIG. 7 is a diagram for explaining control of X-ray energy according to the second embodiment. FIG. 8 is a diagram for explaining control of X-ray energy according to the second embodiment. FIG. 9 is a diagram for explaining control of X-ray energy according to the second embodiment. FIG. 10 is a diagram for explaining control of X-ray energy according to the third embodiment. FIG. 11 is a diagram for explaining control of X-ray energy according to the third embodiment. FIG. 12 is a block diagram showing an example configuration of an X-ray CT apparatus according to the fifth embodiment. FIG. 13A is a diagram illustrating an example of a DAS according to the fifth embodiment; FIG. 13B is a diagram illustrating an example of a DAS according to the fifth embodiment; FIG. 14 is a diagram showing an example of dual energy collection using a sequential collection DAS according to the fifth embodiment. FIG. 15 is a diagram showing an example of dual energy collection using a simultaneous collection DAS according to the fifth embodiment. FIG. 16 is a diagram showing an example of dual energy collection using a sequential collection DAS according to the fifth embodiment. FIG. 17 is a diagram for explaining adjustment of the number of columns of the detection element group according to the fifth embodiment. FIG. 18A is a diagram for explaining setting of tube current values according to the fifth embodiment. FIG. 18B is a diagram for explaining setting of tube current values according to the fifth embodiment. FIG. 18C is a diagram for explaining setting of tube current values according to the fifth embodiment. FIG. 19A is a diagram for explaining setting of tube voltage values according to the fifth embodiment. FIG. 19B is a diagram for explaining setting of tube voltage values according to the fifth embodiment. FIG. 20 is a diagram for explaining adjustment of the number of channels in the detection element group according to the fifth embodiment. FIG. 21 is a diagram showing an example of dual energy collection using a sequential collection DAS according to the fifth embodiment. FIG. 22 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus according to the fifth embodiment. FIG. 23 is a diagram for explaining an example of allowable time control according to the sixth embodiment. FIG. 24 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus according to the sixth embodiment. FIG. 25 is a diagram for explaining an example of allowable time control according to the seventh embodiment. FIG. 26 is a diagram for explaining an example of allowable time control according to the seventh embodiment. FIG. 27 is a diagram for explaining an example of allowable time control according to the seventh embodiment. FIG. 28 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus according to the seventh embodiment. FIG. 29 is a diagram for explaining an example of allowable time control according to the eighth embodiment. FIG. 30 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus according to the eighth embodiment. FIG. 31 is a block diagram showing an example of the configuration of an imaging planning apparatus according to the ninth embodiment.

Hereinafter, embodiments of an X-ray CT apparatus and an imaging planning apparatus will be described in detail with reference to the drawings.

(First embodiment)
The configuration of an X-ray CT apparatus 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a block diagram showing an example configuration of an X-ray CT apparatus 1 according to the first embodiment. As shown in FIG. 1, the X-ray CT apparatus 1 has a gantry device 10, a bed device 30, and a console device 40. As shown in FIG.

In FIG. 1, the rotation axis of the rotating frame 13 or the longitudinal direction of the top plate 33 of the bed apparatus 30 in the non-tilt state is the Z-axis direction. Further, the axial direction perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction. Also, the axial direction perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. Note that FIG. 1 illustrates the gantry 10 from a plurality of directions for explanation, and shows the case where the X-ray CT apparatus 1 has one gantry 10 .

The gantry device 10 has an X-ray tube 11 , an X-ray detector 12 , a rotating frame 13 , an X-ray high voltage device 14 , a control device 15 , a wedge 16 , a collimator 17 and a DAS 18 .

The X-ray tube 11 is a vacuum tube having a cathode (filament) that generates thermoelectrons and an anode (target) that generates X-rays upon collision with thermoelectrons. The X-ray tube 11 emits thermal electrons from the cathode to the anode by applying a high voltage from the X-ray high voltage device 14, thereby generating X-rays to be irradiated to the subject P. As shown in FIG. For example, the X-ray tube 11 is a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermal electrons. Note that the X-ray tube 11 is an example of an X-ray generator.

The X-ray detector 12 detects X-rays emitted from the X-ray tube 11 and passed through the subject P, and outputs a signal corresponding to the detected X-ray dose to the DAS 18 . The X-ray detector 12 has, for example, a plurality of detector element arrays in which a plurality of detector elements are arranged in the channel direction along one circular arc centered on the focal point of the X-ray tube 11 . The X-ray detector 12 has, for example, a structure in which a plurality of detector element arrays each having a plurality of detector elements arranged in the channel direction are arranged in the column direction (slice direction, row direction). Also, the X-ray detector 12 is, for example, an indirect conversion type detector having a grid, a scintillator array, and a photosensor array. The scintillator array has a plurality of scintillators. The scintillator has a scintillator crystal that outputs a photon amount of light corresponding to the amount of incident X-rays. The grid is arranged on the surface of the scintillator array on the X-ray incident side and has an X-ray shielding plate that absorbs scattered X-rays. Note that the grid may also be called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has a function of converting the amount of light from the scintillator into an electrical signal, and has photosensors such as photodiodes, for example. The X-ray detector 12 may be a direct conversion type detector having a semiconductor element that converts incident X-rays into electrical signals. Also, the X-ray detector 12 is an example of an X-ray detection unit.

The rotating frame 13 is an annular frame that supports the X-ray tube 11 and the X-ray detector 12 so as to face each other and rotates the X-ray tube 11 and the X-ray detector 12 by the control device 15 . For example, the rotating frame 13 is a casting made of aluminum. In addition to the X-ray tube 11 and the X-ray detector 12, the rotating frame 13 can also support the X-ray high voltage device 14, the wedge 16, the collimator 17, the DAS 18, and the like. Additionally, the rotating frame 13 may further support various configurations not shown in FIG. Hereinafter, in the gantry device 10, the rotating frame 13 and the portion that rotates together with the rotating frame 13 are also referred to as a rotating portion.

The X-ray high-voltage device 14 has electric circuits such as a transformer and a rectifier, and includes a high-voltage generator that generates a high voltage to be applied to the X-ray tube 11 and an X-ray that the X-ray tube 11 generates. and an X-ray controller for controlling the output voltage according to. The high voltage generator may be of a transformer type or an inverter type. The X-ray high-voltage device 14 may be provided on the rotating frame 13 or may be provided on a fixed frame (not shown).

The control device 15 has a processing circuit having a CPU (Central Processing Unit) and the like, and drive mechanisms such as motors and actuators. The control device 15 receives an input signal from the input interface 43 and controls the operations of the gantry device 10 and the bed device 30 . For example, the control device 15 controls the rotation of the rotating frame 13, the tilt of the gantry device 10, the motions of the bed device 30 and the tabletop 33, and the like. As an example, the control device 15 rotates the rotating frame 13 about an axis parallel to the X-axis direction based on input inclination angle (tilt angle) information as control for tilting the gantry device 10 . Note that the control device 15 may be provided in the gantry device 10 or may be provided in the console device 40 .

Wedge 16 is a filter for adjusting the dose of X-rays emitted from X-ray tube 11 . Specifically, the wedge 16 transmits and attenuates the X-rays irradiated from the X-ray tube 11 so that the X-rays irradiated from the X-ray tube 11 to the subject P have a predetermined distribution. It is a filter that For example, the wedge 16 is a wedge filter or a bow-tie filter, which is a filter made of aluminum or the like so as to have a predetermined target angle and a predetermined thickness.

The collimator 17 is a lead plate or the like for narrowing down the irradiation range of the X-rays transmitted through the wedge 16, and a slit is formed by combining a plurality of lead plates or the like. Note that the collimator 17 may also be called an X-ray diaphragm. 1 shows the case where the wedge 16 is arranged between the X-ray tube 11 and the collimator 17, the case where the collimator 17 is arranged between the X-ray tube 11 and the wedge 16 good too. In this case, the wedge 16 transmits and attenuates the X-rays emitted from the X-ray tube 11 and whose irradiation range is limited by the collimator 17 .

The DAS 18 collects X-ray signals detected by each detection element of the X-ray detector 12 . For example, the DAS 18 has an amplifier that amplifies an electrical signal output from each detection element and an A/D converter that converts the electrical signal into a digital signal, and generates detection data. DAS 18 is implemented by, for example, a processor. Note that the DAS 18 is an example of a collection unit.

Here, the DAS 18 sequentially collects X-ray signals detected by a plurality of detection elements for each view. For example, the DAS 18 is connected to each of a plurality of detection elements via a switch, and sequentially reads the charge integrated by each detection element while switching the detection element to be connected to ON.

An example of sequential collection in the DAS 18 will be described below. For convenience of explanation, sequential collection by four detection elements will be described, but the number of detection elements to which the DAS 18 is connected is not limited to this. For example, the DAS 18 is connected to each of the four detection elements 12a, 12b, 12c, and 12d via switches. In this case, the DAS 18 first turns on the connection with the detection element 12a, and reads out the charges integrated by the detection element 12a as the X-ray signal S11.

Next, the DAS 18 turns off the connection with the detection element 12a, turns on the connection with the detection element 12b, and reads the charges integrated by the detection element 12b as the X-ray signal S12. When the connection with the DAS 18 is turned off, the detection element 12a starts integrating charges.

Next, the DAS 18 turns off the connection with the detection element 12b, turns on the connection with the detection element 12c, and reads the charge integrated by the detection element 12c as an X-ray signal S13. When the connection with the DAS 18 is turned off, the detection element 12b starts integrating charges.

Next, the DAS 18 turns off the connection with the detection element 12c, turns on the connection with the detection element 12d, and reads the charges integrated by the detection element 12d as the X-ray signal S14. When the connection with the DAS 18 is turned off, the detection element 12c starts to integrate charges. Also, after reading the signal S14, the DAS 18 turns off the connection with the detection element 12d. As a result, the detection element 12d starts to integrate charges.

Thus, the DAS 18 provides four signals (signal S11, signal S12, signal S13 and signal S14) is collected sequentially. Similarly, DAS 18 sequentially acquires four signals from four detector elements in subsequent views. In other words, DAS 18 sequentially acquires, for each view, four signals of x-rays detected by four detector elements.

Although the detection element 12a, the detection element 12b, the detection element 12c, and the detection element 12d have been described, the number of multiple detection elements corresponding to the DAS 18 is not limited to "four". For example, the DAS 18 sequentially collects X-ray signals detected by all detector elements in the X-ray detector 12 for each view. In this case, the X-ray CT apparatus 1 has one DAS 18, for example.

Also, for example, the DAS 18 sequentially collects, for each view, X-ray signals detected by a plurality of detection elements (detection element arrays) arranged along the channel direction in the X-ray detector 12 . Alternatively, the DAS 18 sequentially collects, for each view, X-ray signals detected by a plurality of detection elements (detection element rows) arranged along the row direction in the X-ray detector 12 . In this case, the X-ray CT apparatus 1 includes, for example, the same number of DASs 18 as the detector element arrays in the X-ray detector 12 .

Below, in the X-ray detector 12, a plurality of detection elements corresponding to one DAS 18 are also referred to as a detection element group. That is, the X-ray detector 12 has one or more detection element groups. The X-ray CT apparatus 1 also includes one or a plurality of DASs 18 that sequentially collect X-ray signals detected by the detection element group for each view.

The data generated by the DAS 18 is transmitted from a transmitter having a light emitting diode (LED) provided on the rotating frame 13 to a non-rotating portion (for example, a fixed frame, etc.) of the gantry 10 by optical communication. (not shown) is transmitted to a receiver having a photodiode and transferred to the console device 40 . Here, the non-rotating portion is, for example, a fixed frame or the like that rotatably supports the rotating frame 13 . The method of transmitting data from the rotating frame 13 to the non-rotating portion of the gantry 10 is not limited to optical communication, and any non-contact data transmission method may be employed. I don't mind if you hire me.

The bed device 30 is a device for placing and moving a subject P to be scanned, and has a base 31 , a bed driving device 32 , a top board 33 and a support frame 34 . The base 31 is a housing that supports the support frame 34 so as to be vertically movable. The bed drive device 32 is a drive mechanism that moves the table 33 on which the subject P is placed in the longitudinal direction of the table 33, and includes a motor, an actuator, and the like. A top plate 33 provided on the upper surface of the support frame 34 is a plate on which the subject P is placed. Note that the bed driving device 32 may move the support frame 34 in the longitudinal direction of the top plate 33 in addition to the top plate 33 .

The console device 40 has a memory 41 , a display 42 , an input interface 43 and a processing circuit 44 . Although the console device 40 is described as being separate from the gantry device 10 , the console device 40 or a part of each component of the console device 40 may be included in the gantry device 10 .

The memory 41 is implemented by, for example, a RAM (Random Access Memory), a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like. The memory 41 stores projection data and reconstructed image data, for example. Also, for example, the memory 41 stores a program for the circuit included in the X-ray CT apparatus 1 to realize its function. Note that the memory 41 may be realized by a server group (cloud) connected to the X-ray CT apparatus 1 via a network.

The display 42 displays various information. For example, the display 42 displays image data generated by the processing circuit 44, GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display 42 is a liquid crystal display or a CRT (Cathode Ray Tube) display. The display 42 may be of a desktop type, or may be configured by a tablet terminal or the like capable of wireless communication with the main body of the console device 40 .

The input interface 43 receives various input operations from the operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 44 . For example, the input interface 43 allows the operator to input acquisition conditions for acquiring projection data, reconstruction conditions for reconstructing CT image data, image processing conditions for generating post-processed images from CT image data, and the like. accept from For example, the input interface 43 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad that performs input operations by touching the operation surface, a touch screen that integrates a display screen and a touch pad, and an optical sensor. It is realized by the used non-contact input circuit, voice input circuit, or the like. Note that the input interface 43 may be provided in the gantry device 10 . Also, the input interface 43 may be composed of a tablet terminal or the like capable of wireless communication with the main body of the console device 40 . Also, the input interface 43 is not limited to having physical operation parts such as a mouse and a keyboard. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the console device 40 and outputs this electrical signal to the processing circuit 44 is an example of the input interface 43. included.

A processing circuit 44 controls the operation of the entire X-ray CT apparatus 1 . Note that the processing circuit 44 is not limited to being included in the console device 40 . For example, the processing circuit 44 may be included in an integrated server that collectively processes detection data acquired by a plurality of medical image diagnostic apparatuses.

For example, processing circuitry 44 performs system control function 441 , preprocessing function 442 , generation function 443 and output function 444 . Note that the system control function 441 is an example of a control unit. For example, the processing circuit 44 reads out a program corresponding to the system control function 441 from the memory 41 and executes it, thereby executing various functions of the processing circuit 44 based on an input operation received from the operator via the input interface 43. Control.

The system control function 441 also controls the X-ray CT apparatus 1 to perform positioning imaging. For example, the system control function 441 fixes the position of the X-ray tube 11 at a predetermined rotation angle, and irradiates the subject P with X-rays from the X-ray tube 11 while moving the top plate 33 in the Z direction. Perform positioning shooting. Further, the processing circuit 44 reads out a program corresponding to the generation function 443 from the memory 41 and executes it to generate positioning image data based on the X-ray signals collected by positioning imaging. Note that the positioning image data may also be called scanogram image data or scout image data.

Also, the system control function 441 controls the X-ray CT apparatus 1 to perform the main scan. For example, the system control function 441 sets scan conditions (for example, scan range, tube current, etc.) for the main scan based on the positioning image data. Next, the system control function 441 moves the subject P into the imaging port of the gantry device 10 by controlling the bed driving device 32 . Also, the system control function 441 adjusts the aperture and position of the collimator 17 . Also, the system control function 441 rotates the rotating portion by controlling the control device 15 .

Also, the system control function 441 supplies a high voltage to the X-ray tube 11 by controlling the X-ray high voltage device 14 . As a result, the X-ray tube 11 generates X-rays with which the subject P is irradiated. Here, the system control function 441 performs dual energy collection or multi-energy collection. That is, the system control function 441 changes the energy of X-rays generated by the X-ray tube 11 for each one or more views. For example, the system control function 441 changes the energy of X-rays generated by the X-ray tube 11 by controlling the tube voltage supplied to the X-ray tube 11 . The X-ray energy control by the system control function 441 will be described later.

While the main scan is executed by the system control function 441, the DAS 18 sequentially collects X-ray signals detected by the plurality of detection elements for each view and generates detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 by reading out a program corresponding to the preprocessing function 442 from the memory 41 and executing it. For example, the preprocessing function 442 performs preprocessing such as logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, and beam hardening correction on the detection data output from the DAS 18 . Data after preprocessing is also referred to as raw data. Further, detection data before preprocessing and raw data after preprocessing are collectively referred to as projection data.

Also, the generation function 443 generates CT image data based on the corrected raw data. Specifically, the generation function 443 performs reconstruction processing using the filtered back projection method, the iterative reconstruction method, or the like on the corrected raw data to generate CT image data. In addition, the generation function 443 converts the generated CT image data into tomographic image data or three-dimensional image data of an arbitrary cross section by a known method based on the input operation received from the operator via the input interface 43. . The generation function 443 also causes the memory 41 to store the converted tomographic image data and three-dimensional image data.

Further, the processing circuit 44 reads a program corresponding to the output function 444 from the memory 41 and executes it to output tomographic image data, three-dimensional image data, CT image data, and the like. For example, the processing circuit 44 causes the display 42 to display tomographic image data and three-dimensional image data. In addition, for example, the processing circuit 44 transfers tomographic image data, three-dimensional image data, and CT image data to an external device (for example, a server device that stores image data) connected to the X-ray CT apparatus 1 via a network. output to

In the X-ray CT apparatus 1 shown in FIG. 1, each processing function is stored in the memory 41 in the form of a computer-executable program. The processing circuit 44 is a processor that implements a function corresponding to each program by reading the program from the memory 41 and executing the program. In other words, the processing circuit 44 in a state where each program has been read has a function corresponding to the read program. Note that FIG. 1 shows a case where the processing functions of the system control function 441, the preprocessing function 442, the generation function 443, and the output function 444 are realized by a single processing circuit 44, but the embodiment is not limited to this. It is not limited. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may implement each processing function by executing each program. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated in a single or a plurality of processing circuits and implemented.

An example of the configuration of the X-ray CT apparatus 1 has been described above. With this configuration, the X-ray CT apparatus 1 enables dual energy acquisition or multi-energy acquisition by a high-speed switching method using the sequential acquisition DAS 18 . Specifically, the DAS 18 in the X-ray CT apparatus 1 sequentially collects X-ray signals detected by a plurality of detection elements in the X-ray detector 12 for each view. In addition, the system control function 441 in the X-ray CT apparatus 1 controls the energy of X-rays detected by each of the plurality of detection elements at the time of generation to be constant among the detection elements for each one or a plurality of views. The x-ray energy is varied for one or more views. Processing performed by the X-ray CT apparatus 1 according to the first embodiment will be described in detail below.

In addition, in this embodiment, the case where dual energy collection is performed will be described as an example. Further, in the present embodiment, as an example, the X-ray CT apparatus 1 includes a plurality of DASs 18, and each of the DASs 18 includes n detection elements (detection elements 121 . . . , detection elements 12m . . , the case of successively acquiring X-ray signals detected by the detection elements 12n) will be described.

Among the plurality of detection elements, the plurality of detection elements 121 from which X-ray signals are collected substantially simultaneously by each of the plurality of DASs 18 is also referred to as a first detection element group. Among the plurality of detection elements, the plurality of detection elements 12n from which X-ray signals are collected substantially simultaneously by the plurality of DASs 18 are also referred to as the n-th detection element group. n is an integer of 2 or more.

In CT scanning, the X-ray tube 11 generates X-rays while rotating facing the X-ray detector 12 under the control of the system control function 441 . At this time, the detection elements in the X-ray detector 12 detect the X-rays that have passed through the subject P. As shown in FIG. The DAS 18 also collects X-ray signals detected by the detector elements.

Signal collection by the DAS 18 and X-ray energy control by the system control function 441 will be described below with reference to FIG. In FIG. 2, the horizontal axis corresponds to the column direction and the vertical axis corresponds to time. Energy E1 and energy E2 shown in FIG. 2 are energies at the time of X-ray generation. Note that the energy E1 and the energy E2 are different values. Also, the X-ray irradiation time shown in FIG. 2 indicates the time during which each detection element is irradiated with X-rays. Note that FIG. 2 is a diagram for explaining the control of X-ray energy according to the first embodiment.

As shown in FIG. 2, DAS 18 sequentially acquires n signals of x-rays detected by n detector elements for each view. Specifically, the DAS 18 sequentially acquires X-ray signals from time As11 to time Ae11. Also, the DAS 18 sequentially acquires X-ray signals from time As12 to time Ae12 in the next view. Also, the DAS 18 sequentially acquires X-ray signals from time As13 to time Ae13 in the next view.

More specifically, at time As11, the DAS 18 reads and amplifies the charge integrated by the detection element 121 among the n detection elements arranged along the column direction, and performs A/D conversion. . That is, the DAS 18 collects X-ray signals detected by the detection element 121 at time As11. Furthermore, after time As11, the DAS 18 successively collects X-ray signals detected by the detection elements such as the detection element 12m. Then, the DAS 18 collects the X-ray signal detected by the detection element 12n at time Ae11.

As described above, DAS 18 acquires X-ray signals from time As11 to time Ae11. For example, the DAS 18 reads charges from any detection element from time As11 to time Ae11. Alternatively, the DAS 18 performs amplification processing of any detection element from time As11 to time Ae11. Alternatively, the DAS 18 performs A/D conversion of any detection element from time As11 to time Ae11. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is collecting X-ray signals (from time As11 to time Ae11), as shown in FIG.

Also, at time Is11 after time Ae11, the system control function 441 generates X-rays with energy E1. Then, the system control function 441 generates X-rays with energy E1 from time Is11 to time Ie11, and then stops the generation of X-rays. For example, the system control function 441 generates pulsed X-rays with energy E1 from time Is11 to time Ie11. That is, the system control function 441 generates pulsed X-rays while the DAS 18 is not collecting X-ray signals. For example, system control function 441 generates pulsed X-rays while DAS 18 is not performing A/D conversion.

For example, the system control function 441 acquires the timing of signal acquisition by the DAS 18 prior to starting scanning. For example, the system control function 441 acquires time information such as time As11, time Ae11, time As12, time Ae12, time As13, and time Ae13 in FIG. To give another example, the system control function 441 determines the length of time during which the DAS 18 acquires X-ray signals in one view (the length of time As11 to time Ae11, etc.) as the timing of signal acquisition by the DAS 18. , and the period of X-ray signal acquisition (the length of time As11 to time As12, etc.). Then, the system control function 441 generates X-rays according to the timing of signal acquisition by the DAS 18 or stops the generation of X-rays.

Next, the DAS 18 collects X-ray signals from time As12 after time Ie11 to time Ae12. Here, the system control function 441 stops X-ray generation while the DAS 18 is collecting X-ray signals (from time As12 to time Ae12). For example, system control function 441 stops the generation of x-rays while DAS 18 is performing A/D conversion of any detector element. At time Is12 after time Ae12, the system control function 441 generates X-rays with energy E2. For example, the system control function 441 changes the energy setting of the X-rays generated from the X-ray tube 11 while stopping the generation of X-rays (for example, from time Ie11 to time Is12). Change to energy E2. The system control function 441 also controls the X-ray high voltage device 14 to apply a tube voltage to the X-ray tube 11 according to the changed settings. Then, the X-ray tube 11 generates X-rays with energy E2 at time Is12. Further, the system control function 441 stops the generation of X-rays after generating X-rays with energy E2 from time Is12 to time Ie12. Furthermore, the DAS 18 performs A/D conversion of any detection element from time As13 after time Ie12 to time Ae13.

As shown in FIG. 2, system control function 441 stops x-ray generation while DAS 18 is performing A/D conversion of any detector element for each view. In other words, the system control function 441 generates X-rays only during the period when all the detection elements (the detection elements 121 . . . , the detection elements 12m . As a result, the energy at the time of generation of the X-rays detected by each detector element is constant between the detector elements for each view.

For example, in the view (view V11) corresponding to time As11 to time Ae12, generation of X-rays is stopped from time As11 to time Is11 and from time Ie11 to time Ae12. None of the detector elements are exposed to X-rays. On the other hand, from time Is11 to time Ie11, all of the plurality of detection elements are irradiated with X-rays of energy E1.

In this case, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is the product of the X-ray irradiation time (the time from Is11 to Ie11) and the energy E1 in any of the detection elements. Become. That is, in view V11, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements.

Similarly, in the view corresponding to time As12 to time Ae13 (hereinafter referred to as view V12), generation of X-rays is stopped from time As12 to time Is12 and from time Ie12 to time Ae13. , none of the plurality of detector elements is irradiated with X-rays. On the other hand, from time Is12 to time Ie12, all of the plurality of detection elements are irradiated with X-rays of energy E2.

In this case, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is the product of the X-ray irradiation time (the time from Is12 to Ie12) and the energy E2 in any detection element. Become. That is, in the view V12, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements.

As shown in FIG. 2, the system control function 441 controls the energy of the X-rays detected by each of the plurality of detection elements at the time of generation to be constant between the detection elements for each view. changes for each view. For example, the system control function 441 generates X-rays of energy E1 or X-rays of energy E2 for each view, as shown in FIG. That is, by changing the energy of the X-rays as shown in FIG. 2, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

Further, the DAS 18 generates detection data based on the signals of the dual-energy acquired X-rays and outputs the generated detection data to the processing circuitry 44 . Next, the preprocessing function 442 preprocesses the detected data. The generation function 443 also generates CT image data based on the preprocessed projection data, and utilizes the fact that X-ray absorption characteristics differ for each substance to identify the substance contained in the subject P. A process for discriminating types, atomic numbers, densities, etc. (hereinafter referred to as discrimination processing) is executed. Note that the discrimination process may be performed by an external device. For example, the output function 444 outputs projection data (detection data before preprocessing or raw data after preprocessing) to an external device connected to the X-ray CT apparatus 1 via a network. However, the external device may perform the discrimination processing.

In FIG. 2, time Ie11 and time As12 are shown as approximately the same time, but time Ie11 may be earlier than time As12. Also, in FIG. 2, the time Is12 and the time Ae12 are shown to be approximately the same, but the time Is12 may be a time later than the time Ae12. For example, system control function 441 may stop the generation of x-rays for a longer period of time than while DAS 18 is A/D converting any detector element. Further, the system control function 441 may shield the X-rays irradiated to the X-ray detector 12 by controlling the collimator 17 instead of stopping the generation of X-rays. That is, the system control function 441 stops X-ray irradiation to the X-ray detector 12 at least while the DAS 18 is performing A/D conversion of any detection element.

In addition, the system control function 441 considers that residual components due to the incident X-rays can be detected in the detecting element even after the X-ray irradiation is stopped, so that the DAS 18 starts A/D conversion. Therefore, X-ray irradiation to the X-ray detector 12 may be stopped. In this case, the system control function 441 first acquires the length of time for which residual components due to incident X-rays are detected in the detection elements.

For example, if the X-ray detector 12 is an indirect conversion type detector, the X-ray detector 12 has a scintillator that converts X-rays into light and a photodiode that detects the converted light. Here, while X-rays are being irradiated, charges generated in the photodiode may be trapped in internal trap levels. After the X-ray irradiation is stopped, the charges trapped in the trap levels may be detected as residual components of the incident X-rays.

For example, in calibration, the system control function 441 measures the length of time L1 during which the residual component due to the incident X-rays is detected in the detection element after the X-ray irradiation is stopped, and measures the measured length L1. store L1 in memory 41; Also, the system control function 441 acquires the length of time L1 from the memory 41 prior to the start of scanning. In addition, while the DAS 18 is performing A/D conversion of any of the detection elements, the system control function 441 starts from the point of time L1 or more before the DAS 18 starts A/D conversion: X-ray irradiation is also stopped until the DAS 18 starts A/D conversion.

In FIG. 2, the X-ray irradiation to the X-ray detector 12 is stopped while the DAS 18 is performing A/D conversion of at least one of the detection elements for each view. However, embodiments are not so limited. For example, as shown in FIG. 3, the system control function 441 controls X-ray irradiation to the X-ray detector 12 for each view at least while the DAS 18 is performing A/D conversion of one of the detection elements. It may be stopped or the X-ray energy may be kept constant. Note that FIG. 3 is a diagram for explaining the control of X-ray energy according to the first embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As21 to time Ae21. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (from time As21 to time Ae21).

Also, at time Is21 after time Ae21, the system control function 441 generates X-rays with energy E1. Next, DAS 18 sequentially performs A/D conversion from time As22 to time Ae22. Here, the system control function 441 maintains the X-ray energy constant at energy E1 while the DAS 18 is performing A/D conversion of any of the detection elements (between time As22 and time Ae22). do.

Next, the system control function 441 stops generation of X-rays with energy E1 at time Ie21 before time As23. That is, the system control function 441 generates X-rays with energy E1 from time Is21 to time Ie21. Next, DAS 18 sequentially performs A/D conversion from time As23 to time Ae23. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (from time As23 to time Ae23).

Here, in a view corresponding to time As21 to time Ae22 (hereinafter referred to as view V21), the energy at the time of generation of X-rays detected by each of the plurality of detection elements is not constant among the detection elements. For example, in view V21, the energy at the time of generation of X-rays detected by the detection element 121 is the product of the X-ray irradiation time (time from Is21 to As22) and energy E1. On the other hand, the generated energy of the X-ray detected by the detection element 12n is the product of the X-ray irradiation time (the time from Is21 to Ae22) and the energy E1. Here, since the time from Is21 to As22 and the time from Is21 to Ae22 are different in length, the energy at the time of generation of the X-rays detected by the detection element 121 and the X-rays detected by the detection element 12n is different from the energy at the time of generation. Similarly, in the view corresponding to time As22 to time Ae23 (hereinafter referred to as view V22), the energy at the time of generation of X-rays detected by each of the plurality of detection elements is not constant among the detection elements.

However, when looking at two views (view V21 and view V22) in FIG. 3, the energy at the time of generation of the X-rays detected by each of the plurality of detector elements is constant among the detector elements.

For example, the energy at the time of generation of the X-ray detected by the detector element 121 is the product of the time from time Is21 to time As22 and the energy E1 in view V21, and the energy E1 from time As22 to time Ie21 in view V22. It is the product of time and energy E1. Therefore, in the two views (view V21 and view V22), the energy at the time of occurrence of the X-rays detected by the detector element 121 is equal to the product of the time from time Is21 to time Ie21 and the energy E1.

Similarly, in the two views (view V21 and view V22), the energy at the time of generation of the X-ray detected by each of the plurality of detector elements is the time from time Is21 to time Ie21 and It is the product of energy E1. That is, in two views (view V21 and view V22), the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant between the detection elements.

Next, the system control function 441 generates X-rays with energy E2 at time Is22 after time Ae23. Also, the DAS 18 sequentially performs A/D conversion from time As24 to time Ae24. Also, the DAS 18 sequentially performs A/D conversion from time As25 to time Ae25. Also, the DAS 18 sequentially performs A/D conversion from time As26 to time Ae26. Here, the system control function 441 controls the DAS 18 to perform A/D conversion of any of the detection elements (from time As24 to time Ae24, from time As25 to time Ae25, and from time As26 to Until time Ae26), the X-ray energy is kept constant at energy E2.

Next, the system control function 441 stops generation of X-rays with energy E2 at time Ie22 before time As27. That is, the system control function 441 generates X-rays with energy E2 from time Is22 to time Ie22. Next, DAS 18 sequentially performs A/D conversion from time As27 to time Ae27. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (between time As27 and time Ae27).

Hereinafter, the view corresponding to time As23 to time Ae24 will be referred to as view V23. A view corresponding to time As24 to time Ae25 is assumed to be view V24. A view corresponding to time As25 to time Ae26 is assumed to be view V25. A view corresponding to time As26 to time Ae27 is assumed to be view V26. As shown in FIG. 3, in view V23, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is not constant among the detector elements. In view V26, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is not constant among the detection elements.

However, when looking at the four views (view V23, view V24, view V25 and view V26) in FIG. It has become. Specifically, in these four views, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is the time from time Is22 to time Ie22 and the energy E2 at any detector element. product. That is, in these four views, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is constant among the detector elements.

As shown in FIG. 3, the system control function 441 controls the energy of X-rays detected by each of the plurality of detector elements at the time of generation to be constant among the detector elements for each of the plurality of views, while controlling the X-ray Vary the energy of each of the multiple views. For example, the system control function 441 generates X-rays of energy E1 in views V21 and V22, and X-rays of energy E2 in views V23, V24, V25 and V26.

For example, the DAS 18 performs addition processing of X-ray signals for each of a plurality of views so that the energy of the X-rays detected by each of the plurality of detection elements at the time of generation is constant among the detection elements, and outputs detected data. to generate Alternatively, DAS 18 generates detection data based on the acquired x-ray signals for each view. In this case, the processing circuit 44 or an external device that executes the discrimination process performs preprocessing for the discrimination process so that the energy at the time of generation of the X-rays detected by each of the plurality of detection elements is constant among the detection elements. Then, X-ray signals are added for each of a plurality of views. That is, by changing the X-ray energy as shown in FIG. 3, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

In FIG. 3, the case where the difference in integration timing in each detection element is small has been described. As a result, in FIG. 3, after the A/D conversion by the DAS 18 is completed in one view, it takes a certain amount of time (for example, from time Ae21 to time As22 to start A/D conversion by the DAS 18 in the next view). time) is occurring. However, embodiments are not so limited.

That is, the difference in integration timing in each detection element may be larger than in the case shown in FIG. For example, after the DAS 18 finishes A/D conversion in one view, it immediately starts A/D conversion in the next view, as shown in FIG. Note that FIG. 4 is a diagram for explaining the control of X-ray energy according to the first embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As31 to time Ae31. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (from time As31 to time Ae31).

Also, at time Is31, which is the same as time Ae31, the system control function 441 generates X-rays with energy E1. Also, the DAS 18 sequentially performs A/D conversion from time As32, which is the same time as time Ae31 and time Is31, to time Ae32. Here, the system control function 441 maintains the X-ray energy constant at energy E1 while the DAS 18 is performing A/D conversion of any of the detection elements (from time As32 to time Ae32). do.

Next, the system control function 441 stops generation of X-rays with energy E1 at time Ie31 which is the same as time Ae32. That is, the system control function 441 generates X-rays with energy E1 from time Is31 to time Ie31. Also, the DAS 18 sequentially performs A/D conversion from time As33, which is the same time as time Ae32 and time Ie31, to time Ae33. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (from time As33 to time Ae33).

Next, the system control function 441 generates X-rays of energy E2 at time Is32 which is the same as time Ae33. In addition, the DAS 18 sequentially performs A/D conversion from time As34, which coincides with time Ae33 and time Is32, to time Ae34. The DAS 18 sequentially performs A/D conversion from time As35, which is the same time as time Ae34, to time Ae35. The DAS 18 sequentially performs A/D conversion from time As36, which is the same as time Ae35, to time Ae36. Here, the system control function 441 maintains the X-ray energy constant at energy E2 while the DAS 18 is performing A/D conversion of any of the detection elements (from time As34 to time Ae36). do.

Next, the system control function 441 stops generation of X-rays with energy E2 at time Ie32, which is the same as time Ae36. That is, the system control function 441 generates X-rays with energy E2 from time Is32 to time Ie32. Next, the DAS 18 sequentially performs A/D conversion from time As37, which coincides with time Ae36 and time Ie32, to time Ae37. Here, the system control function 441 stops the generation of X-rays while the DAS 18 is performing A/D conversion of any detection element (from time As37 to time Ae37).

Hereinafter, the view corresponding to time As31 to time Ae32 will be referred to as view V31. A view corresponding to time As32 to time Ae33 is assumed to be view V32. A view corresponding to time As33 to time Ae34 is assumed to be view V33. A view corresponding to time As34 to time Ae35 is assumed to be view V34. A view corresponding to time As35 to time Ae36 is assumed to be view V35. A view corresponding to time As36 to time Ae37 is assumed to be view V36. As shown in FIG. 4, in view V31, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is not constant among the detector elements. Similarly, in view V32, the energies at the time of generation of the X-rays detected by each of the plurality of detector elements are not constant among the detector elements. Similarly, in view V33, the energy at the time of generation of the X-rays detected by each of the multiple detector elements is not constant among the detector elements. Similarly, in view V36, the energies at the time of generation of the X-rays detected by each of the plurality of detector elements are not constant among the detector elements.

However, when looking at two views (view V31 and view V32) in FIG. 4, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is constant among the detector elements. Similarly, looking at the four views (view V33, view V34, view V35 and view V36), the energy at the time of generation of the X-rays detected by each of the plurality of detector elements is constant among the detector elements. there is

As shown in FIG. 4, the system control function 441 controls the energy of X-rays detected by each of the plurality of detector elements at the time of generation to be constant among the detector elements for each of the plurality of views, while controlling the X-ray Vary the energy of each of the multiple views. For example, the system control function 441 generates X-rays of energy E1 in views V31 and V32, and X-rays of energy E2 in views V33, V34, V35 and V36. In other words, the system control function 441 can execute dual energy collection by the high-speed switching method using the DAS 18 of the sequential collection method even when there is a large deviation in the integration timing of each detection element.

Next, an example of the procedure of processing by the X-ray CT apparatus 1 will be described with reference to FIG. FIG. 5 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus 1 according to the first embodiment. Steps S101 , S102 , S103 , S104 , S105 , S106 , S107 , S108 and S109 are steps corresponding to the system control function 441 .

First, the processing circuit 44 acquires the timing of A/D conversion by the DAS 18 prior to the start of scanning (step S101). Next, the processing circuit 44 determines whether or not an instruction to start scanning has been received from the operator (step S102). Here, if the instruction to start scanning is not accepted (No at step S102), the processing circuit 44 enters a standby state.

On the other hand, if an instruction to start scanning has been received (Yes at step S102), the processing circuit 44 rotates the rotating section around the subject P and controls the X-ray high-voltage device 14 to transmit the X-ray to the X-ray tube 11. A high voltage is supplied and X-rays are irradiated (step S103). For example, the processing circuitry 44 causes the subject P to be irradiated with X-rays of energy E1 or energy E2.

Next, the processing circuitry 44 determines whether or not to stop X-ray irradiation (step S104). For example, the processing circuit 44 determines whether or not to stop X-ray irradiation before the DAS 18 starts A/D conversion based on the A/D conversion timing acquired in step S101. . For example, the processing circuit 44 executes the determination process of step S104 once per view.

If it is determined not to stop X-ray irradiation (No at step S104), the processing circuit 44 proceeds to step S103 again to continue X-ray irradiation. That is, processing circuitry 44 keeps the energy of the x-rays constant. On the other hand, if it is determined to stop the X-ray irradiation (Yes at step S104), the processing circuit 44 stops the X-ray irradiation (step S105). Here, the processing circuit 44 determines whether or not to end scanning (step S106).

If the scan is not to end (No at step S106), the processing circuit 44 determines whether or not to change the energy of the X-ray (step S107). If the energy of the X-ray is to be changed (Yes at step S107), the processing circuitry 44 changes the energy setting of the X-ray to be generated from the X-ray tube 11 (step S108). If the X-ray energy is not changed (No at step S107), or after step S108, the processing circuit 44 determines whether or not to start X-ray irradiation (step S109). Here, when it is determined not to start X-ray irradiation (No at step S109), the processing circuit 44 enters a standby state. On the other hand, if it is determined to start X-ray irradiation (Yes at step S109), the processing circuit 44 proceeds to step S103 again, applies a tube voltage according to the setting to the X-ray tube 11, and emits X-rays. irradiate. Here, if it is determined in step S107 to change the energy of the X-rays, the processing circuit 44 irradiates X-rays with energy different from that of the previous view. On the other hand, if it is determined in step S107 not to change the X-ray energy, the processing circuit 44 irradiates the X-ray with the same energy as the previous view. If it is determined to end scanning (Yes at step S107), the processing circuit 44 ends the process.

As described above, according to the first embodiment, the X-ray tube 11 generates X-rays. In addition, the X-ray detector 12 has one or more detection element groups composed of a plurality of detection elements for detecting X-rays. The DAS 18 sequentially collects X-ray signals detected by a plurality of detector elements for each view. The system control function 441 adjusts the energy of the X-rays to one or more so that the energy at the time of generation of the X-rays detected by each of the plurality of detection elements is constant among the detection elements for each of one or more views. change for each view. Therefore, the X-ray CT apparatus 1 according to the first embodiment can perform dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

That is, the system control function 441 periodically changes the energy of the X-rays irradiated to the subject P, and while acquiring the detection data for one or a plurality of consecutive views, the system control function 441 irradiates the subject P. The X-ray tube 11 is controlled such that the average X-ray energy is substantially equal among the first to n-th detection element groups. As a result, the X-ray CT apparatus 1 can use the DAS 18 of the sequential acquisition system to perform dual energy acquisition by the high-speed switching system.

It should be noted that the fact that the averages of the X-ray energies are substantially equal includes not only cases where the averages are equal but also cases where the averages differ to some extent. For example, there may be cases where it is difficult to always equalize the average X-ray energies among the first to n-th detection element groups due to technical restrictions on hardware or software. Further, for example, a case is assumed in which control is performed to intentionally change the average energy of X-rays among the first to n-th detection element groups. In this way, even when there is a difference in the average X-ray energies among the first to n-th detection element groups, the control for making the average X-ray energies substantially equal is included.

It should be noted that it is also possible to perform dual energy collection by a fast switching method using a simultaneous collection DAS. For example, as shown in FIG. 6, X-ray signals are simultaneously collected from n detection elements (detection element 121, detection element 12m, detection element 12n) by using a simultaneous acquisition DAS. Thus, the X-ray irradiation time with the same energy can be made constant within the integration time of each detection element. That is, by using n DASs, it is possible to make the energy at the time of generation of X-rays detected by each of the n detection elements constant among the detection elements. FIG. 6 is a diagram for explaining the simultaneous collection DAS according to the first embodiment.

However, as described above, when using the simultaneous acquisition DAS, the number of DASs corresponding to the number of detection elements of the X-ray detector 12 is required. For example, if the X-ray detector 12 has "1000" detection elements in the channel direction and "200" detection elements in the column direction, "200000" simultaneous collection DASs are required. Furthermore, as the number of DASs increases, not only the number of amplifiers and A/D converters in the DASs, but also the number of conductors connecting the DASs and detection elements increases, resulting in an increase in the scale of the circuit. As a result, when using a simultaneous collection DAS, the cost increases, or implementation becomes difficult due to space constraints.

On the other hand, the X-ray CT apparatus 1 uses the sequential acquisition system DAS 18 to enable dual energy acquisition by a high-speed switching system. For example, when one DAS 18 sequentially acquires X-ray signals detected by a plurality of detection elements arranged along the column direction (detection elements for one column), the X-ray CT apparatus 1 It suffices to provide as many DASs 18 as the number of columns (the number of detection elements in the channel direction) in the detector 12 . For example, if the X-ray detector 12 has "1000" detection elements in the channel direction and "200" detection elements in the column direction, the X-ray CT apparatus 1 may include "1000" DASs 18. It will be good. Therefore, the X-ray CT apparatus 1 enables dual energy acquisition by the high-speed switching system, and also uses the DAS 18 of the sequential acquisition system to reduce the size of the circuit and reduce the cost.

In addition, as shown in FIG. 4, the system control function 441 can perform dual energy collection by a high-speed switching method using the DAS 18 of the sequential collection method even when there is a large deviation in the integration timing of each detection element. can. Here, the case where the difference in integration timing in each detection element is large is, for example, the case where the number of detection elements connected to one DAS 18 is large. Therefore, the system control function 441 can perform dual energy collection by fast switching even when many sensing elements are connected to one DAS 18 and the circuit is kept smaller.

(Second embodiment)
In the above-described first embodiment, a case has been described in which the X-ray energy is changed for each view by changing the X-ray energy before and after the X-ray irradiation is stopped. For example, in FIGS. 2, 3, and 4, the case where X-rays with energy E1 are emitted, X-rays with energy E2 is emitted after the X-rays are stopped, is described. On the other hand, in the second embodiment, a case will be described in which the energy of X-rays is changed for each view by changing the energy of X-rays while irradiating X-rays.

The X-ray CT apparatus 1 according to the second embodiment has the same configuration as the X-ray CT apparatus 1 shown in FIG. Hereinafter, the same reference numerals as those in FIG. 1 are assigned to the same configurations as those described in the first embodiment, and descriptions thereof are omitted.

For example, the system control function 441 changes the energy of X-rays between energy E1 and energy E2 while irradiating X-rays, as shown in FIG. Here, FIG. 7 is a diagram for explaining control of X-ray energy according to the second embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As41 to time Ae41. Also, the DAS 18 sequentially performs A/D conversion from time As42 to time Ae42. Here, the system control function 441 keeps the energy of the X-ray constant at the energy E1 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As41 to time Ae42 is hereinafter referred to as view V41. Note that the view V41 is an example of a first view.

Also, the system control function 441 changes the energy of the X-rays from energy E1 to energy E2 from time Cs41 after time Ae42 to time Ce41 before time As43. That is, after the DAS 18 finishes A/D conversion in the view V41, the system control function 441 continues until the DAS 18 starts A/D conversion in the next view V42 (view corresponding to time As42 to time Ae43). to change the energy of the X-rays. Note that the view V42 is an example of a second view.

Next, the DAS 18 sequentially performs A/D conversion from time As43 to time Ae43. Also, the DAS 18 sequentially performs A/D conversion from time As44 to time Ae44. Also, the DAS 18 sequentially performs A/D conversion from time As45 to time Ae45. Also, the DAS 18 sequentially performs A/D conversion from time As46 to time Ae46. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view (view V45) corresponding to time As45 to time Ae46 is an example of the third view.

As shown in FIG. 7, in the view (view V41) corresponding to time As41 to time Ae42, the X-ray irradiation time of X-ray irradiation with energy E1 is constant for each detector element. That is, in view V41, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements. Similarly, in the view (view V43) corresponding to time As43 to time Ae44, the view (view V44) corresponding to time As44 to time Ae45, and the view V45, X-rays detected by each of the plurality of detection elements The energy at generation is constant between detector elements from view to view. That is, by changing the X-ray energy as shown in FIG. 7, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

Depending on the time required to change the X-ray energy, after the DAS 18 completes A/D conversion in the first view and before the DAS 18 starts A/D conversion in the next view, It is conceivable that the change in X-ray energy is not complete. In this case, the system control function 441, as shown in FIG. 8, after the DAS 18 completes A/D conversion in one view, until the DAS 18 starts A/D conversion in a view subsequent to the next view. In between, the X-ray energy is changed. FIG. 8 is a diagram for explaining control of X-ray energy according to the second embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As51 to time Ae51. Also, the DAS 18 sequentially performs A/D conversion from time As52 to time Ae52. Here, the system control function 441 keeps the energy of the X-ray constant at the energy E1 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As51 to time Ae52 is hereinafter referred to as view V51. Note that the view V51 is an example of the first view.

Next, the system control function 441 starts changing the X-ray energy from energy E1 toward energy E2 at time Cs51 after time Ae52. Next, DAS 18 sequentially performs A/D conversion from time As53 to time Ae53. Then, the DAS 18 changes the X-ray energy to energy E2 at time Ce51 before time As54. That is, after the DAS 18 completes the A/D conversion in the view V51, the system control function 441 selects the view V53 (corresponding to the time As53 to the time Ae54) after the next view V52 (the view corresponding to the time As52 to the time Ae53). The energy of the X-rays is changed until the DAS 18 starts A/D conversion in the view shown in FIG. Note that the view V53 is an example of a second view.

Next, DAS 18 sequentially performs A/D conversion from time As54 to time Ae54. Also, the DAS 18 sequentially performs A/D conversion from time As55 to time Ae55. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view (view V54) corresponding to time As54 to time Ae55 is an example of the third view.

As shown in FIG. 8, in the view (view V51) corresponding to time As51 to time Ae52, the X-ray irradiation time of X-rays with energy E1 is constant for each detector element. That is, the energy at the time of generation of X-rays detected by each of the plurality of detection elements in the view V51 is constant among the detection elements. Similarly, in view V54, the energy at the time of generation of X-rays detected by each of the plurality of detector elements is constant among the detector elements for each view. That is, by changing the X-ray energy as shown in FIG. 8, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

In FIG. 8, a view (such as view V51) in which signals are acquired using X-rays of energy E1 and a view (such as view V54) in which signals are acquired using X-rays of energy E2 are repeated one by one. explained the case. However, embodiments are not so limited. For example, as shown in FIG. 9, the system control function 441 alternates between a view in which signals are acquired using X-rays of energy E1 and two views in which signals are acquired using X-rays of energy E2. may Note that FIG. 9 is a diagram for explaining the control of X-ray energy according to the second embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As61 to time Ae61. Also, the DAS 18 sequentially performs A/D conversion from time As62 to time Ae62. Here, the system control function 441 keeps the energy of the X-ray constant at the energy E1 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As61 to time Ae62 is hereinafter referred to as view V61. Note that the view V61 is an example of the first view.

Next, the system control function 441 starts changing the X-ray energy from energy E1 toward energy E2 at time Cs61 after time Ae62. Next, DAS 18 sequentially performs A/D conversion from time As63 to time Ae63. Then, the DAS 18 changes the X-ray energy to energy E2 at time Ce61 before time As64. That is, after the DAS 18 completes the A/D conversion in the view V61, the system control function 441 selects the view V63 (corresponding to the time As63 to the time Ae64) after the next view V62 (the view corresponding to the time As62 to the time Ae63). The energy of the X-rays is changed until the DAS 18 starts A/D conversion in the view shown in FIG. Note that the view V63 is an example of a second view.

Next, DAS 18 sequentially performs A/D conversion from time As64 to time Ae64. Also, the DAS 18 sequentially performs A/D conversion from time As65 to time Ae65. Also, the DAS 18 sequentially performs A/D conversion from time As66 to time Ae66. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view (view V65) corresponding to time As65 to time Ae66 is an example of the third view.

As shown in FIG. 9, in the view (view V61) corresponding to time As61 to time Ae62, the X-ray irradiation time of X-rays with energy E1 is constant for each detector element. That is, in view V61, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements. Similarly, in the view corresponding to time As64 to time Ae65 (view V64) and view V65, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is is constant. That is, by changing the X-ray energy as shown in FIG. 9, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

Furthermore, the system control function 441 can change the number of views in which the signal is acquired using X-rays of energy E1 and the number of views in which the signal is acquired using X-rays of energy E2, thereby increasing the number of data for each energy. Differences in accuracy can be reduced. That is, in views where signals are acquired using high-energy X-rays (hereinafter referred to as high-energy views), the acquired projection data has high image quality, and the data can be obtained with high accuracy. On the other hand, in views where signals are acquired using low-energy X-rays (hereinafter referred to as low-energy views), data accuracy is relatively low.

On the other hand, the system control function 441 increases the number of low-energy views over the number of high-energy views so that the accuracy of the projection data corresponding to the low-energy views is reduced to the projection data corresponding to the high-energy views. You can get closer to the accuracy of your data. For example, if the energy E1 is higher than the energy E2, the system control function 441, as shown in FIG. By repeating the acquisition of the two views, it is possible to reduce the difference in accuracy between the projection data corresponding to the energy E1 and the projection data corresponding to the energy E2.

That is, the system control function 441 increases or decreases the number of views according to the level of energy, thereby reducing the difference in data accuracy caused by the level of energy. The system control function 441 may similarly increase or decrease the number of views according to the level of energy in the control of FIGS. 2, 3, 4, 7, and the like.

As described above, after the DAS 18 completes A/D conversion in the first view, the system control function 441 according to the second embodiment causes the DAS 18 to perform A/D conversion in the second view after the first view. The X-ray energy is changed until the D conversion is started. In addition, the system control function 441 controls at least while the DAS 18 is performing A/D conversion of any detector element in a plurality of views from the second view to the third view after the second view. , keeping the energy of the X-ray constant. Therefore, the X-ray CT apparatus 1 according to the second embodiment can change the energy of X-rays while irradiating X-rays to perform dual energy acquisition by a high-speed switching method.

Here, the generation of X-rays by the X-ray tube 11 generally does not stop at the moment when the supply of the tube voltage to the X-ray tube 11 is stopped. Therefore, in order to stop X-ray irradiation to the X-ray detector 12, X-ray cutoff may be required. For example, the system control function 441 performs tube voltage control of the X-ray tube 11 in consideration of the time from when the supply of the tube voltage is stopped to when the generation of X-rays is stopped. to cut off the X-rays and stop irradiation of the X-rays to the X-ray detector 12 .

On the other hand, the system control function 441 according to the second embodiment changes the X-ray energy while irradiating X-rays. Therefore, the system control function 441 can change the energy of the X-rays for each one or more views without cutting off the X-rays to perform fast-switching dual-energy acquisition.

(Third embodiment)
In the above-described first and second embodiments, by using X-rays with either energy E1 or energy E2 in one view, when X-rays detected by each of the plurality of detection elements are generated The case where the energy at is constant among the detection elements has been described. On the other hand, in the third embodiment, the X-ray energy is changed in one view, and the energy at the time of generation of the X-rays detected by each of the plurality of detection elements is made constant among the detection elements. A case will be described.

The X-ray CT apparatus 1 according to the third embodiment has the same configuration as the X-ray CT apparatus 1 shown in FIG. Hereinafter, the same reference numerals as those in FIG. 1 are assigned to the same configurations as those described in the first embodiment, and descriptions thereof are omitted.

For example, the DAS 18 sequentially performs A/D conversion from time As71 to time Ae71, as shown in FIG. Next, DAS 18 sequentially performs A/D conversion from time As72 to time Ae72. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. Note that FIG. 10 is a diagram for explaining the control of X-ray energy according to the third embodiment. The view corresponding to time As71 to time Ae72 is hereinafter referred to as view V71. Note that the view V71 is an example of a first view.

Next, the system control function 441 changes the energy of the X-rays from energy E2 to energy E1 during a period from time Cs71 after time Ae72 to time Ce71. Next, the system control function 441 keeps the X-ray energy constant at the energy E1 from time Ce71 to time Cs72. Next, the system control function 441 changes the energy of X-rays from energy E1 to energy E2 from time Cs72 to time Ce72 before time As73. Next, the DAS 18 sequentially performs A/D conversion from time As73 to time Ae73. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As72 to time Ae73 is hereinafter referred to as view V72. Note that the view V72 is an example of a second view.

As shown in FIG. 10, the system control function 441 changes the X-ray energy from energy E2 to energy E1 after time Ae72 until time As73, and then from energy E1 to energy E2. Let That is, the system control function 441 controls the X-ray energy to be After changing from the energy E2 to the energy E1, the energy E1 is changed to the energy E2. As a result, the energy at the time of generation of the X-rays detected by each detector element is constant between the detector elements for each view.

First, in the view V71, the X-ray irradiation time during which X-rays of energy E2 are irradiated is constant for each detection element. That is, in view V71, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements.

Next, in view V72, the irradiation time of X-rays with energy E2 is constant for each detector element. Specifically, in the view V72, the X-ray irradiation time of X-rays with energy E2 is the length of time for the DAS 18 to perform A/D conversion (from time As73 to time Ae73 is equal to the length of time until Alternatively, if there is a time lag from time Ae72 to time Cs71 or a time lag from time Ce72 to time As73, the X-ray irradiation time during which X-rays with energy E2 are irradiated is equal to the DAS 18 of A/ It is equal to the sum of the length of time for D conversion and these time lags.

In addition, while the X-ray energy is changing (the time from time Cs71 to time Ce71 and the time from time Cs72 to time Ce72), none of the plurality of detection elements receives X-ray irradiation. there is Moreover, during the time from time Ce71 to time Cs72, all of the plurality of detection elements are irradiated with X-rays of energy E1. As described above, in view V72, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant among the detection elements.

As shown in FIG. 10, the system control function 441 controls the energy of X-rays detected by each of the plurality of detection elements at the time of generation to be constant between the detection elements for each view. changes for each view. That is, by changing the X-ray energy as shown in FIG. 10, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

In FIG. 10, after the DAS 18 completes A/D conversion in the first view, the X-ray energy is changed to energy The case where the energy E1 is changed to the energy E2 after the energy E2 is changed to the energy E1 has been described. However, embodiments are not so limited.

For example, as shown in FIG. 11, after the DAS 18 completes A/D conversion in the first view, the system control function 441 causes the DAS 18 to perform A/D conversion in views subsequent to the first view. , the X-ray energy may be changed from energy E2 to energy E1 and then from energy E1 to energy E2. Note that FIG. 11 is a diagram for explaining the control of X-ray energy according to the third embodiment.

For example, the DAS 18 sequentially performs A/D conversion from time As81 to time Ae81, as shown in FIG. Next, DAS 18 sequentially performs A/D conversion from time As82 to time Ae82. Next, DAS 18 sequentially performs A/D conversion from time As83 to time Ae83. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As81 to time Ae82 is hereinafter referred to as view V81. A view corresponding to time As82 to time Ae83 is assumed to be view V82. Note that the view V82 is an example of a first view.

Next, the system control function 441 changes the energy of X-rays from energy E2 to energy E1 during a period from time Cs81 after time Ae83 to time Ce81.
Next, DAS 18 sequentially performs A/D conversion from time As84 to time Ae84. Here, the system control function 441 keeps the X-ray energy constant at the energy E1 from time Ce81 to time Cs82. The view corresponding to time As83 to time Ae84 is hereinafter referred to as view V83.

Next, the system control function 441 changes the energy of X-rays from energy E1 to energy E2 from time Cs82 to time Ce82 before time As85. Next, DAS 18 sequentially performs A/D conversion from time As85 to time Ae85. Here, the system control function 441 keeps the energy of the X-ray constant at energy E2 at least while the DAS 18 is performing A/D conversion of any detection element. The view corresponding to time As84 to time Ae85 is hereinafter referred to as view V84. Note that the view V84 is an example of a second view.

As shown in FIG. 10, the system control function 441 changes the X-ray energy from energy E2 to energy E1 after time Ae83 until time As85, and then from energy E1 to energy E2. Let That is, the system control function 441 controls the X-ray energy to be After changing from the energy E2 to the energy E1, the energy E1 is changed to the energy E2. As a result, the energy at the time of generation of the X-rays detected by each detector element is constant between the detector elements for each view.

First, in the view V81, the X-ray irradiation time during which X-rays of energy E2 are irradiated is constant for each detection element. Similarly, in view V82, the X-ray irradiation time of X-rays with energy E2 is constant for each detector element. That is, in the views V81 and V82, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant between the detection elements for each view.

Next, looking at the two views, view V83 and view V84, the X-ray irradiation time of X-rays with energy E2 is constant for each detector element. Specifically, in these two views, the X-ray exposure time of exposure to X-rays of energy E2 is equal to the length of time during which the DAS 18 performs A/D conversion in any detector element. Alternatively, if there is a time lag from time Ae83 to time Cs81 or a time lag from time Ce82 to time As85, the X-ray irradiation time during which X-rays of energy E2 are irradiated is equal to the DAS 18 of A/ It is equal to the sum of the length of time for D conversion and these time lags.

In addition, while the X-ray energy is changing (the time from time Cs81 to time Ce81 and the time from time Cs82 to time Ce82), none of the plurality of detection elements receive X-ray irradiation. there is Moreover, during the time from time Ce81 to time Cs82, all of the plurality of detection elements are irradiated with X-rays of energy E1. As described above, in the two views of view V83 and view V84, the energy at the time of generation of X-rays detected by each of the plurality of detection elements is constant between the detection elements.

As shown in FIG. 11, the system control function 441 controls the energy of X-rays detected by each of the plurality of detector elements at the time of generation to be constant among the detector elements for each of one or more views. , varying the energy of the x-rays for one or more views. That is, by changing the X-ray energy as shown in FIG. 11, the system control function 441 can execute dual energy acquisition by the high-speed switching method using the DAS 18 of the sequential acquisition method.

(Fourth embodiment)
Although the first to third embodiments have been described so far, various different modes other than the above-described first to third embodiments may be implemented.

In the above-described first to third embodiments, as an example of the period during which the DAS 18 is collecting X-ray signals, the period during which the DAS 18 is performing A/D conversion of any of the detection elements has been described. However, embodiments are not so limited. For example, the system control function 441 controls the operation of the DAS 18 while the DAS 18 is collecting X-ray signals, while the DAS 18 is reading charges from any of the detection elements, or while the DAS 18 is amplifying any of the detection elements. The duration of processing may be used to control the energy of the x-rays. For example, the system control function 441 stops X-ray irradiation to the X-ray detector 12 for each view, at least while the DAS 18 is reading charges from any detector element. To give another example, the system control function 441 stops X-ray irradiation to the X-ray detector 12 for each view, at least while the DAS 18 is performing amplification processing of any detection element.

Further, in the first to third embodiments described above, the case of performing dual energy acquisition has been described, but it is also possible to perform multi-energy acquisition using X-rays of three or more different energies. . For example, the system control function 441 stops X-ray irradiation to the X-ray detector 12 at least while the DAS 18 is collecting X-ray signals, Or, X-rays of energy E3 different from energy E1 and energy E2 are generated for each view. This allows the system control function 441 to use X-rays of three different energies to perform multi-energy acquisition by a fast switching method.

Further, in the first to third embodiments described above, a single-tube type X-ray CT apparatus has been described as an example of the X-ray CT apparatus 1 . However, the embodiment is not limited to this, and the X-ray CT apparatus 1 is a so-called multi-tube type X-ray CT apparatus in which a plurality of pairs of X-ray tubes and X-ray detectors are mounted on a rotating ring. It may be a device.

For example, the X-ray CT apparatus 1 has a pair of a first X-ray tube and a first X-ray detector and a pair of a second X-ray tube and a second X-ray detector. In addition, the X-ray CT apparatus 1 includes a first DAS that sequentially collects X-ray signals detected by a plurality of detection elements in the first X-ray detector for each view; and a second DAS that sequentially acquires X-ray signals detected by the plurality of detector elements for each view.

In this case, the system control function 441, for example, stops X-ray irradiation to the first X-ray detector while at least the first DAS is collecting X-ray signals, and reduces the energy E1. X-rays or X-rays of energy E2 are generated for each view. Further, the system control function 441 stops irradiation of X-rays to the second X-ray detector at least while the second DAS is collecting X-ray signals, and X-rays of energy E3, Alternatively, X-rays of energy E4 different from energy E1, energy E2 and energy E3 are generated for each view. This allows the system control function 441 to use X-rays of four different energies to perform multi-energy acquisition by a fast switching method.

(Fifth embodiment)
When DE acquisition or ME acquisition is performed by high-speed switching using a sequential acquisition DAS, the X-ray tube requires more time than when DE acquisition or ME acquisition is performed by high-speed switching using a simultaneous acquisition DAS. The allowable time for switching the supplied tube voltage value tends to be short. As a result, when DE acquisition or ME acquisition is performed by high-speed switching using a sequential acquisition DAS, the imaging conditions (tube voltage value, tube current value, etc.) that can be set may be limited.

Therefore, the X-ray CT apparatus 1 according to the fifth embodiment performs dual energy acquisition or multi-energy acquisition by high-speed switching using a sequential acquisition system DAS by the processing described below. Increase freedom.

For example, the processing circuit 44 in the X-ray CT apparatus 1 according to the fifth embodiment further executes an adjusting function 445 and a setting function 446, as shown in FIG. Note that the adjustment function 445 is an example of an adjustment unit. Also, the setting function 446 is an example of a setting unit.

For example, the processing circuit 44 reads out a program corresponding to the system control function 441 from the memory 41 and executes it, thereby executing various functions of the processing circuit 44 based on an input operation received from the operator via the input interface 43. Control.

The system control function 441 also controls the X-ray CT apparatus 1 to perform positioning imaging. For example, the system control function 441 fixes the position of the X-ray tube 11 at a predetermined rotation angle, and irradiates the subject P with X-rays from the X-ray tube 11 while moving the top plate 33 in the Z direction. Perform positioning shooting. Further, the processing circuit 44 reads out a program corresponding to the generation function 443 from the memory 41 and executes it to generate positioning image data based on the X-ray signals collected by positioning imaging. Note that the positioning image data may also be called scanogram image data or scout image data.

Also, the system control function 441 controls the X-ray CT apparatus 1 to perform the main scan. Note that the main scan is also simply referred to as photographing. For example, the system control function 441 supplies high voltage to the X-ray tube 11 by controlling the X-ray high voltage device 14 . As a result, the X-ray tube 11 generates X-rays with which the subject P is irradiated. Here, the system control function 441 changes the X-ray energy generated by the X-ray tube 11 for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . That is, the system control function 441 performs dual energy collection or multi-energy collection with fast switching. The X-ray energy control by the system control function 441 will be described later. Further, the system control function 441 moves the subject P into the imaging port of the gantry device 10 by controlling the bed driving device 32 . Also, the system control function 441 adjusts the aperture and position of the collimator 17 . Also, the system control function 441 rotates the rotating portion by controlling the control device 15 .

Also, for example, the processing circuit 44 controls the permissible time for switching the tube voltage value supplied to the X-ray tube 11 by reading out and executing a program corresponding to the adjustment function 445 from the memory 41 . Also, for example, the processing circuit 44 sets the imaging conditions by reading out a program corresponding to the setting function 446 from the memory 41 and executing the program. Note that control of the allowable time and setting of imaging conditions will be described later.

While imaging is performed by the system control function 441, the DAS 18 sequentially collects X-ray signals for each detection element group in the X-ray detector 12 and generates detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 by reading out a program corresponding to the preprocessing function 442 from the memory 41 and executing it. For example, the preprocessing function 442 performs preprocessing such as logarithmic conversion processing, offset correction processing, inter-channel sensitivity correction processing, and beam hardening correction on the detection data output from the DAS 18 . Data after preprocessing is also referred to as raw data. Further, detection data before preprocessing and raw data after preprocessing are collectively referred to as projection data.

Also, the generation function 443 generates CT image data based on the corrected raw data. Specifically, the generation function 443 performs reconstruction processing using the filtered back projection method, the iterative reconstruction method, or the like on the corrected raw data to generate CT image data. In addition, the generation function 443 converts the generated CT image data based on the input operation received from the operator via the input interface 43 to a display CT image (arbitrary cross-sectional tomographic image data, 3D image data, etc.) by a known method. dimensional image data, etc.). The generation function 443 also causes the memory 41 to store the converted CT image for display.

Further, the processing circuit 44 reads a program corresponding to the output function 444 from the memory 41 and executes it to output tomographic image data, three-dimensional image data, CT image data, and the like. For example, the processing circuit 44 causes the display 42 to display tomographic image data and three-dimensional image data. In addition, for example, the processing circuit 44 transfers tomographic image data, three-dimensional image data, and CT image data to an external device (for example, a server device that stores image data) connected to the X-ray CT apparatus 1 via a network. output to

In the X-ray CT apparatus 1 shown in FIG. 12, each processing function is stored in the memory 41 in the form of a computer-executable program. The processing circuit 44 is a processor that implements a function corresponding to each program by reading the program from the memory 41 and executing the program. In other words, the processing circuit 44 in a state where each program has been read has a function corresponding to the read program.

Note that FIG. 12 shows a case where the processing functions of the system control function 441, the adjustment function 445, the setting function 446, the preprocessing function 442, the generation function 443, and the output function 444 are realized by a single processing circuit 44. However, embodiments are not limited to this. For example, the processing circuit 44 may be configured by combining a plurality of independent processors, and each processor may implement each processing function by executing each program. Further, each processing function of the processing circuit 44 may be appropriately distributed or integrated in a single or a plurality of processing circuits and implemented.

Next, the DAS 18 of the sequential collection method will be described. FIG. 13A is a diagram showing an example of a sequential collection DAS 18 according to the fifth embodiment. In FIG. 13A, the DAS 18 sequentially collects X-ray signals from a detection element group consisting of n detection elements (detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12. A case of doing so will be explained. In this case, the X-ray CT apparatus 1 has the same number of channels as the X-ray detector 12, for example, the DAS 18 shown in FIG. 13A. For example, when the number of channels in the X-ray detector 12 is "c", the X-ray CT apparatus 1 includes c DASs 18 from DAS181 to DAS18c as shown in FIG. 13B. DAS181, DAS182, DAS183, DAS184, DAS185, DAS186, and DAS18c shown in FIG. FIG. 13B is a diagram showing an example of the sequential collection DAS 18 according to the fifth embodiment.

In FIG. 13A, the detecting element closest to the DAS 18 among the n detecting elements is the detecting element 121, and the detecting element second closest to the DAS 18 is the detecting element 122. In FIG. Similarly, in FIG. 13A, the n-th closest detector element to DAS 18 (that is, the detector element furthest from DAS 18) is referred to as detector element 12n.

For example, the DAS 18 is connected to each of the detection elements 121 to 12n via a switch, and detects X-rays detected by the detection elements 121 to 12n while the X-ray tube 11 is generating X-rays. Collect the signals sequentially. Specifically, first, the DAS 18 turns on the connection with the detection element 121 and reads the charge integrated by the detection element 121 as an X-ray signal. Next, the DAS 18 turns off the connection with the detection element 121, turns on the connection with the detection element 122, and reads the charge integrated by the detection element 122 as an X-ray signal. Note that when the connection with the DAS 18 is turned off, the detection element 121 starts integrating charges. Similarly, the DAS 18 sequentially reads the charge integrated in each detecting element up to the detecting element 12n as an X-ray signal.

As an example, the DAS 18 sequentially collects n signals in one view from the detector element group consisting of the detector elements 121 to 12n. Similarly, DAS 18 sequentially acquires n signals from detector elements in subsequent views. Although the case of sequentially acquiring X-ray signals for each view has been described, the DAS 18 may sequentially acquire X-ray signals for each of a plurality of views.

Also, although the case where the reading is performed in order from the detecting element 121 to the detecting element 12n has been described, the order of reading is not limited to this. For example, the DAS 18 may first read out the charge integrated in the sensing element 12n and then read out toward the sensing element 121 in sequence.

Further, for example, the DAS 18 may first read out the charges integrated in the intermediate detection elements among the n detection elements, and then sequentially read out the charges toward the detection elements 121 and 12n. That is, the DAS 18 may sequentially read out from the center of the X-ray detector 12 toward the outside.

As an example, when “n” is an even number, the DAS 18 first reads the charge integrated in the detector element located (n/2)th closest to the DAS 18 . The DAS 18 then reads out the charge integrated in the sensing element at the ((n/2)−1)th closest position to the DAS 18 . DAS 18 then reads out the charge integrated in the detector element at the ((n/2)+1)th closest position to DAS 18 . DAS 18 then reads out the charge integrated in the detector element at the ((n/2)-2)th closest position to DAS 18 . Similarly, the DAS 18 sequentially reads the charge integrated in each detecting element up to the detecting element 121 and the detecting element 12n as an X-ray signal.

Also, a case has been described in which X-ray signals are successively collected from the detector element group consisting of n detector elements arranged along the column direction of the X-ray detector 12, but the embodiment is limited to this. isn't it. For example, the DAS 18 may sequentially collect X-ray signals from a group of detector elements arranged along the channel direction of the X-ray detector 12 . In this case, the X-ray CT apparatus 1 has the same number of DASs 18 as the number of columns in the X-ray detector 12, for example. Further, for example, the DAS 18 may be a case in which X-ray signals are sequentially collected from a detection element group consisting of all detection elements of the X-ray detector 12 . In this case, the X-ray CT apparatus 1 has, for example, only one DAS 18 . That is, the X-ray detector 12 has one or more detection element groups. The X-ray CT apparatus 1 also includes one or a plurality of DASs 18 that sequentially acquire X-ray signals for each detection element group.

An example of the configuration of the X-ray CT apparatus 1 has been described above. With this configuration, the X-ray CT apparatus 1 improves the degree of freedom of imaging conditions when executing dual energy acquisition or multi-energy acquisition by high-speed switching using the sequential acquisition system DAS 18 .

Specifically, the system control function 441 changes the X-ray energy for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . That is, the system control function 441 performs dual energy collection or multi-energy collection with fast switching. The DAS 18 also sequentially collects X-ray signals for each detection element group in the X-ray detector 12 . Further, the adjustment function 445 adjusts at least one of the number of columns and the number of channels of the detection element group for signal collection by the DAS 18 to control the allowable time for switching the tube voltage value, thereby increasing the degree of freedom of the imaging conditions. Improve.

Processing performed by the X-ray CT apparatus 1 according to the fifth embodiment will be described in detail below. Note that, in this embodiment, as an example, a case where dual energy collection is performed will be described. Further, in this embodiment, as an example, the X-ray CT apparatus 1 includes a plurality of DASs 18, each of which is connected to n detection elements (detection elements 121 to 12n) arranged along the column direction. I will explain the case where

First, an example of dual energy collection using the DAS 18 will be described with reference to FIG. FIG. 14 is a diagram showing an example of dual energy collection using the sequential collection DAS 18 according to the fifth embodiment. In FIG. 14 , the horizontal axis corresponds to time, and the vertical axis corresponds to the column direction in X-ray detector 12 . Energy E1 and energy E2 shown in FIG. 14 are energies at the time of X-ray generation. Note that the energy E1 and the energy E2 are different values. As an example, a case where the energy E1 is higher than the energy E2 will be described below.

When performing imaging, the system control function 441 supplies a high voltage to the X-ray tube 11 to generate X-rays while rotating the rotating portion. For example, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T111 to time T114 to generate X-rays with energy E1. Further, the system control function 441 changes the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to a value lower than the first tube voltage value V1 during the period from time T114 to time T115. Switch to the second tube voltage value V2.

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T115 to time T118 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T118 to time T119. .

Next, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T119 to time T122 to generate X-rays with energy E1. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T122 to time T123. .

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T123 to time T126 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T126 to time T127. .

As described above, in the case shown in FIG. 14, the system control function 441 switches the X-ray energy every two views by switching the tube voltage value supplied to the X-ray tube 11 . At this time, the detection elements in the X-ray detector 12 detect the X-rays that have passed through the subject P. As shown in FIG. Also, each of the plurality of DASs 18 sequentially acquires signals from detector element groups consisting of n detector elements.

Specifically, the DAS 18 sequentially acquires n signals from the detector elements from time T111 to time T112. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T113 to time T114. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T115 to time T116. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T117 to time T118. Also, the DAS 18 successively acquires n signals from the detection element group from time T119 to time T120. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T121 to time T122. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T123 to time T124. Also, the DAS 18 sequentially acquires n signals from the detection element group from time T125 to time T126.

More specifically, at time T111, the DAS 18 reads and amplifies the charge integrated by the detection element 121 among the n detection elements arranged along the column direction, and performs A/D conversion. . That is, the DAS 18 collects X-ray signals detected by the detection element 121 at time T111. Furthermore, after time T111, the DAS 18 successively collects X-ray signals detected by each detection element. Then, the DAS 18 collects the X-ray signal detected by the detection element 12n at time T112.

Next, the DAS 18 sequentially collects X-ray signals from the detection elements 121 to 12n from time T113 to time T114. Here, the energy at the time of generation of X-rays detected by the detection elements 121 to 12n is constant among the detection elements.

For example, the energy at the time of generation of the X-ray detected by the detector element 121 at time T113 is the product of the time from time T111 to time T113 and the energy E1. Also, the energy at the time of generation of the X-ray detected by the detection element 12n at time T114 is the product of the time from time T112 to time T114 and the energy E1. Here, as shown in FIG. 14, since the time from time T111 to time T113 and the time from time T112 to time T114 are the same, the X-rays detected by the detection elements 121 and 12n are generated. The energy at time becomes constant between detector elements.

Similarly, in the next view (view corresponding to time T115 to time T118), the energy at the time of generation of X-rays detected by each of the detection elements 121 to 12n is constant among the detection elements. It's becoming For example, the energy at the time of generation of the X-ray detected by the detector element 121 at time T117 is the product of the time from time T115 to time T117 and the energy E2. Also, the energy at the time of generation of the X-ray detected by the detection element 12n at time T118 is the product of the time from time T116 to time T118 and the energy E2. Here, as shown in FIG. 14, the time from time T115 to time T117 and the time from time T116 to time T118 are the same, so the generation of X-rays detected by the detection elements 121 and 12n The energy at time becomes constant between detector elements.

Here, as described above, in order to make the energy of the X-ray generation constant between the detecting elements in the view corresponding to time T115 to time T118, the period from time T114 to time T115 shown in FIG. In the meantime, it is necessary to change the energy of X-ray generation from energy E1 to energy E2. That is, the system control function 441 needs to switch the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T114 to time T115. . Note that the time allowed for switching the tube voltage value, such as the period from time T114 to time T115, is also described as an allowable time. In addition, as shown in FIG. 14, the permissible time when signals are sequentially collected from a detection element group consisting of n detection elements is also described as permissible time Ln.

Similarly, in the view corresponding to time T119 to time T122, in order to make the energy of X-ray generation constant between the detection elements, X-ray It is necessary to switch the tube voltage value supplied to the tube 11 from the second tube voltage value V2 to the first tube voltage value V1. Similarly, in the view corresponding to time T123 to time T126, in order to make the energy of the X-ray generated between the detection elements constant, X-ray It is necessary to switch the tube voltage value supplied to the tube 11 from the first tube voltage value V1 to the second tube voltage value V2.

Here, when performing dual energy collection by high-speed switching using the DAS 18 of the sequential collection method, the allowable time is shorter than when performing dual energy collection by high-speed switching using the DAS of the simultaneous collection method. Cheap. In the following description, the DAS of the simultaneous collection method is referred to as DAS 18a.

For example, when performing dual energy acquisition by high-speed switching using the DAS 18a of the simultaneous acquisition method, the system control function 441 sets the first tube voltage value V1 to X It is supplied to the ray tube 11 to generate X-rays of energy E1. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T212 to time T213. . FIG. 15 is a diagram showing an example of dual energy collection using the simultaneous collection type DAS 18a according to the fifth embodiment.

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T213 to time T214 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T214 to time T215. .

Next, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T215 to time T216 to generate X-rays with energy E1. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T216 to time T217. .

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T217 to time T218 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T218 to time T219. .

As shown in FIG. 15, the system control function 441 switches the X-ray energy every two views by switching the tube voltage value supplied to the X-ray tube 11 . At this time, the detection elements in the X-ray detector 12 detect the X-rays that have passed through the subject P. As shown in FIG. Here, the simultaneous acquisition system DAS 18a is provided for each detection element and acquires signals from the corresponding detection element. For example, for n detection elements from the detection element 121 to the detection element 12n, n DASs 18a of the simultaneous collection system are provided. The n DASs 18a then simultaneously acquire signals from the n detector elements.

Specifically, in the case shown in FIG. 15, in the view corresponding to time T211 to time T212, n DASs 18a simultaneously acquire signals from n detector elements from time T211 to time T212. Also, in the view corresponding to time T213 to time T214, n DAS 18a simultaneously acquire signals from n detector elements from time T213 to time T214. Also, in the view corresponding to time T215 to time T216, n DAS 18a simultaneously acquire signals from n detector elements from time T215 to time T216. Also, in the view corresponding to time T217 to time T218, n DAS 18a simultaneously acquire signals from n detector elements from time T217 to time T218.

Here, the energy at the time of generation of X-rays detected by the detection elements 121 to 12n is constant among the detection elements. For example, the energy at the time of generation of X-rays detected by n detector elements in the view corresponding to time T211 to time T212 is the sum of the time from time T211 to time T212 and the energy E1 in any detector element. product and constant.

Even in the case shown in FIG. 15, the system control function 441 must change the X-ray energy within the allowable time. For example, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T212 to time T213. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T214 to time T215. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T216 to time T217. Also, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T218 to time T219.

As shown in FIGS. 14 and 15, when performing dual energy collection by high-speed switching using the sequential collection system DAS 18, it is faster than when executing dual energy collection by high-speed switching using the simultaneous collection system DAS 18a. Shorter allowable time. That is, when performing dual energy collection by high-speed switching using the sequential collection DAS 18, there is a time difference in the timing of collecting signals from the detection elements, and the allowable time is shortened by this time difference.

Here, when the allowable time is shortened, there are cases where the imaging conditions that can be set are limited. For example, the larger the voltage difference between the first tube voltage value V1 and the second tube voltage value V2, the longer it takes to switch the tube voltage values. That is, the settable tube voltage value may be limited due to the shortened allowable time.

Also, in order to lower the tube voltage value, it is necessary to drain electrons from the cathode (filament) of the X-ray tube. need. That is, the lower limit of the tube current value that can be set may be limited due to the shortening of the allowable time. In addition, electrons must be accumulated in the cathode of the X-ray tube in order to increase the tube voltage value. . That is, the upper limit of the settable tube current value may be limited due to the shortening of the allowable time.

Therefore, the adjustment function 445 controls the permissible time by adjusting the number of rows of the detection element groups for which the sequential acquisition system DAS 18 collects signals, and further improves the degree of freedom of imaging conditions. Control of the allowable time by the adjustment function 445 will be described below with reference to FIG. FIG. 16 is a diagram showing an example of dual energy collection using the sequential collection DAS 18 according to the fifth embodiment.

In the case shown in FIG. 16, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T311 to time T314 to generate X-rays with energy E1. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T314 to time T315. .

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T315 to time T318 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T318 to time T319. .

Next, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T319 to time T322 to generate X-rays of energy E1. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T322 to time T323. .

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T323 to time T326 to generate X-rays with energy E2. Further, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T326 to time T327. .

Also, as shown in FIG. 16, the adjustment function 445 adjusts the number of columns of detector elements for which the DAS 18 collects signals. That is, adjustment function 445 reduces the number of columns of detector elements for which DAS 18 collects signals from 'n' to 'm'. Then, the DAS 18 sequentially collects X-ray signals from a detection element group consisting of m detection elements.

Specifically, the DAS 18 sequentially collects m signals from the detection element group consisting of m detection elements from the detection element 121 to the detection element 12m from time T311 to time T312. In addition, the DAS 18 sequentially acquires m signals from the detection element group from time T313 to time T314. Also, the DAS 18 sequentially acquires m signals from the detector elements from time T315 to time T316. In addition, the DAS 18 sequentially acquires m signals from the detection element group from time T317 to time T318. In addition, the DAS 18 sequentially acquires m signals from the detection element group from time T319 to time T320. Also, the DAS 18 sequentially collects m signals from the detection element group from time T321 to time T322. Also, the DAS 18 sequentially collects m signals from the detection element group from time T323 to time T324. In addition, the DAS 18 sequentially acquires m signals from the detection element group from time T325 to time T326.

In FIG. 16, in order to make the energy of the X-rays detected by the detection elements 121 to 12m constant between the detection elements when the X-rays are generated, the system control function 441 sets the first tube voltage It is necessary to complete the switching of the tube voltage value between the value V1 and the second tube voltage value V2 within the allowable time. Note that, as shown in FIG. 16, the permissible time in the case of sequentially collecting signals from a detection element group consisting of m detection elements is also referred to as permissible time Lm.

Specifically, the system control function 441 changes the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T314 to time T315. need to switch to Further, the system control function 441 needs to switch the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T318 to time T319. There is Further, the system control function 441 needs to switch the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2 during the period from time T322 to time T323. There is Further, the system control function 441 needs to switch the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1 during the period from time T326 to time T327. There is

Here, the allowable time Lm shown in FIG. 16 is longer than the allowable time Ln shown in FIG. This is because the number of detection elements for which one DAS 18 sequentially collects signals is reduced from 'n' to 'm', thereby reducing the time difference between the timings for collecting signals from each detection element. Specifically, the allowable time Lm shown in FIG. 16 is longer than the allowable time Ln shown in FIG. 14 by the amount of time required to sequentially collect signals from (nm) detection elements. ing. Therefore, the smaller "m" is, the longer the allowable time Lm is. In other words, the adjustment function 445 can control the allowable time by adjusting the number of columns of the detection element groups for which the DAS 18 collects signals.

In FIG. 16, when the number of columns of the detection element group is adjusted to "m" by the adjustment function 445, the DAS 18 receives X-ray signals from the m detection elements from the detection element 121 to the detection element 12m. The case of sequential collection has been described. That is, with reference to FIG. 16, the case where the X-ray signals are successively collected for m detection elements from the detection element 121 closest to the DAS 18 has been described. However, embodiments are not so limited. For example, the DAS 18 may sequentially collect X-ray signals from m detector elements from the farthest detector element 12 n from the DAS 18 .

Also, for example, the DAS 18 may sequentially acquire signals for m detector elements in the center of the X-ray detector 12 . As an example, if 'n' and 'm' are even numbers, DAS 18 will move the ((n+m)/2) X-ray signals are sequentially collected for m detector elements up to the closest detector element. In this case, the plurality of DASs 18 provided in the X-ray CT apparatus 1 are central regions ( X-ray signals are sequentially collected from the area indicated by the hatched pattern in FIG. 17). Here, the system control function 441 may adjust the aperture and position of the collimator 17 so that only the area of the X-ray detector 12 indicated by the hatched pattern in FIG. 17 is irradiated with X-rays. good. Note that FIG. 17 is a diagram for explaining adjustment of the number of columns of the detection element group according to the fifth embodiment.

As described above, the adjustment function 445 can control the permissible time for switching the tube voltage value by adjusting the number of columns of the detection element group for which the DAS 18 collects signals. Furthermore, the setting function 446 sets the imaging conditions based on the allowable time after control by the adjustment function 445 . Here, the adjustment function 445 can improve the degree of freedom when the setting function 446 sets the imaging conditions by controlling the allowable time.

For example, the setting function 446 sets the tube current value of the X-ray tube 11 based on the allowable time after control by the adjusting function 445 . An example of setting the tube current value will be described below with reference to FIGS. 18A, 18B, and 18C. 18A, 18B, and 18C are diagrams for explaining setting of tube current values according to the fifth embodiment. Note that the horizontal axes of FIGS. 18A, 18B, and 18C indicate time, and the vertical axes indicate tube voltage values.

First, FIG. 18A will be described. FIG. 18A shows the increase in tube voltage value and the The time required for each descent is indicated. In FIG. 18A, the tube voltage value can be increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Ln when the number of columns of the detection element group is "n". It is possible. In FIG. 18A, it is also possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln.

Further, FIG. 18B shows the tube voltage value when the tube current value is "500 mA", the first tube voltage value V1 is "140 kV", and the second tube voltage value V2 is "80 kV". It shows the time required for each of the ascent and descent. That is, FIG. 18B shows a case where the tube current value is smaller than that in FIG. 18A. Therefore, in FIG. 18B, the time required for the tube voltage value to rise is shorter and the time required for the tube voltage value to drop is longer than in the case of FIG. 18A.

In FIG. 18B, the tube voltage value can be increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Ln when the number of columns of the detection element group is "n". It is possible. However, in FIG. 18B, the tube voltage value cannot be decreased from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln.

In FIG. 18B, the tube voltage value is increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Lm when the number of rows of the detection element group is adjusted to "m". It is possible to Furthermore, in FIG. 18B, it is also possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Lm. That is, the setting function 446 can select the tube current value "500 mA" as the imaging condition by the adjustment function 445 controlling the allowable time.

FIG. 18C shows the tube voltage value when the tube current value is "300 mA", the first tube voltage value V1 is "140 kV", and the second tube voltage value V2 is "80 kV". It shows the time required for each of the ascent and descent. That is, FIG. 18C shows a case where the tube current value is even smaller than that in FIG. 18B. Therefore, in FIG. 18C, the time required for the tube voltage value to rise is shorter and the time required for the tube voltage value to drop is longer than in the case of FIG. 18B.

In FIG. 18C, the tube voltage value can be increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Ln when the number of columns of the detection element group is "n". It is possible. However, in FIG. 18C, the tube voltage value cannot be decreased from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln.

In FIG. 18C, the tube voltage value is increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Lm when the number of rows of the detection element group is adjusted to "m". It is possible to Furthermore, in FIG. 18C, it is possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Lm. That is, the setting function 446 can select the tube current value "300 mA" as the imaging condition by the adjustment function 445 controlling the allowable time.

As shown in FIG. 18C, when the tube current value is "300 mA", the time required to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 and the allowable time Lm has approximately the same length. Here, if the tube current value is further decreased from "300 mA", the time required for the tube voltage value to decrease becomes even longer. Therefore, if the tube current value is further decreased from "300 mA", the tube voltage value cannot be decreased from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Lm.

Therefore, the setting function 446 sets a value of "300 mA" or more as the tube current value. That is, the setting function 446 sets the lower limit of the selectable tube current value based on the allowable time after control by the adjusting function 445, and sets the tube current value of the X-ray tube 11 so as to exceed the set lower limit. do.

Here, the setting function 446 may newly set the tube current value of the X-ray tube 11, or may set the tube current value by changing preset conditions set in advance. For example, when setting a new tube current value, the setting function 446 causes the display 42 to display the lower limit of selectable tube current values, and accepts an input operation of the tube current value from the operator. When the operator inputs a value exceeding the lower limit, the setting function 446 sets the input value as the tube current value of the X-ray tube 11 .

Further, for example, when the tube current value is set by changing the preset conditions, the setting function 446 displays the preset conditions on the display 42 and accepts an operation to change the preset conditions from the operator. Here, the setting function 446 accepts an operation to change the preset condition within a range not below the lower limit of the selectable tube current value. The setting function 446 sets the preset condition changed by the operator as the tube current value of the X-ray tube 11 .

Similarly, as the tube current value increases, the time required for the tube voltage value to rise increases. from the tube voltage value V2 to the first tube voltage value V1. Therefore, the setting function 446 sets the upper limit of the selectable tube current value based on the allowable time after the control by the adjusting function 445, and sets the tube current value of the X-ray tube 11 so as to fall below the set upper limit. It is also possible to

Next, a case of setting the tube voltage value supplied to the X-ray tube 11 as an imaging condition will be described with reference to FIGS. 19A and 19B. 19A and 19B are diagrams for explaining setting of tube voltage values according to the fifth embodiment. Note that the horizontal axis in FIGS. 19A and 19B indicates time, and the vertical axis indicates the tube voltage value.

First, FIG. 19A will be described. FIG. 19A shows the increase in tube voltage value and the The time required for each descent is indicated. That is, FIG. 19A shows a case where the first tube voltage value V1 is higher and the second tube voltage value V2 is lower than in FIG. 18B.

That is, FIG. 19A shows a case where the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is large compared to FIG. 18B. Specifically, the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is "60 kV" in FIG. 18B, and the first tube voltage value V1 and the second tube voltage value V2 in FIG. The voltage difference between the tube voltage value V2 is "80 kV". Therefore, in FIG. 19A, both the time required for the tube voltage value to rise and the time required for the tube voltage value to drop are longer than in the case of FIG. 18B.

In FIG. 19A, the tube voltage value can be increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Ln when the number of columns of the detection element group is "n". It is possible. However, in FIG. 19A, the tube voltage value cannot be lowered from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln.

Further, in FIG. 19A, the tube voltage value is increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Lm when the number of rows of the detection element group is adjusted to "m". It is possible to Furthermore, in FIG. 19A, it is also possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Lm. That is, the adjustment function 445 controls the allowable time so that the setting function 446 can select "150 kV" as the first tube voltage value and "70 kV" as the second tube voltage value. It's becoming That is, the adjustment function 445 controls the allowable time, so that the setting function 446 can select a combination of "150 kV" and "70 kV" as the tube voltage value to be supplied to the X-ray tube 11. there is

Further, FIG. 19B shows the tube voltage value when the tube current value is "500 mA", the first tube voltage value V1 is "160 kV", and the second tube voltage value V2 is "60 kV". It shows the time required for each of the ascent and descent. That is, FIG. 19B shows a case where the first tube voltage value V1 is higher and the second tube voltage value V2 is lower than in FIG. 19A.

That is, FIG. 19B shows a case where the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is larger than that in FIG. 19A. Specifically, in FIG. 19B, the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is "100 kV". Therefore, in FIG. 19B, both the time required for the tube voltage value to rise and the time required for the tube voltage value to drop are longer than in the case of FIG. 19A.

In FIG. 19B, it is possible to increase the tube voltage value from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Ln when the number of columns of the detection element group is "n". It is possible. However, in FIG. 19B, the tube voltage value cannot be lowered from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln.

In FIG. 19B, the tube voltage value is increased from the second tube voltage value V2 to the first tube voltage value V1 within the allowable time Lm when the number of rows of the detection element group is adjusted to "m". It is possible to Furthermore, in FIG. 19B, it is possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Lm. That is, the adjustment function 445 controls the allowable time so that the setting function 446 can select "160 kV" as the first tube voltage value and "60 kV" as the second tube voltage value. It's becoming That is, the setting function 446 can select a combination of "160 kV" and "60 kV" as the tube voltage value to be supplied to the X-ray tube 11 by the adjustment function 445 controlling the allowable time. there is

As shown in FIG. 19B, when the first tube voltage value is "160 kV" and the second tube voltage value is "60 kV", the tube voltage value is changed from the first tube voltage value V1 to the 2 and the allowable time Lm are approximately the same length. Here, if the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is further increased from "100 kV", the time required for the tube voltage value to drop becomes even longer. Therefore, if the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is further increased from "100 kV", the tube voltage value will increase to the first tube voltage value V1 within the allowable time Lm. to the second tube voltage value V2.

Therefore, the setting function 446 sets the tube voltage value within a range in which the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 does not exceed "100 kV". That is, the setting function 446 sets the upper limit of the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 based on the allowable time after the control by the adjustment function 445, and the set upper limit The first tube voltage value V1 and the second tube voltage value V2 are set so as to be less than .

Here, the setting function 446 may newly set the tube voltage value, or may set the tube voltage value by changing preset conditions that have been set in advance. For example, when setting a new tube voltage value, the setting function 446 causes the display 42 to display the upper limit of the selectable voltage difference, and the operator inputs the first tube voltage value V1 and the second tube voltage value V2. accepts the input operation of Then, when the voltage difference between the input first tube voltage value V1 and the second tube voltage value V2 is below the upper limit, the setting function 446 supplies the input value to the X-ray tube 11. Set as the tube voltage value to be used.

Further, for example, when the tube voltage value is set by changing the preset conditions, the setting function 446 displays the preset conditions on the display 42 and accepts an operation to change the preset conditions from the operator. Here, the setting function 446 accepts an operation to change the preset condition within a range not exceeding the upper limit of the selectable voltage difference. The setting function 446 sets the preset condition changed by the operator as the tube voltage value of the X-ray tube 11 .

Note that not only the voltage difference between the first tube voltage value V1 and the second tube voltage value V2, but also the magnitudes of the first tube voltage value V1 and the second tube voltage value V2 are the tube voltage values. May affect the time it takes to descend. For example, as shown in FIG. 19B, when the first tube voltage value V1 is "160 kV" and the second tube voltage value V2 is "60 kV", the tube voltage value is set to the first tube voltage value. The time required for decreasing the voltage value V1 to the second tube voltage value V2 and the allowable time Lm are substantially the same length. Here, for example, when the first tube voltage value V1 is "150 kV" and the second tube voltage value V2 is "50 kV", the difference between the first tube voltage value V1 and the second tube voltage value V2 is Although the voltage difference between them remains "100 kV", the decrease in the first tube voltage value V1 and the second tube voltage value V2 lengthens the time required for the tube voltage value to drop. Therefore, when the first tube voltage value V1 is "150 kV" and the second tube voltage value V2 is "50 kV", the tube voltage value is changed from the first tube voltage value V1 to the second 2 tube voltage value V2.

Therefore, the setting function 446 not only determines the voltage difference between the first tube voltage value V1 and the second tube voltage value V2, but also the magnitude of the first tube voltage value V1 and the second tube voltage value V2. , the tube voltage value to be supplied to the X-ray tube 11 may be set. For example, the setting function 446 decreases the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 for each combination of the first tube voltage value V1 and the second tube voltage value V2. A table defining the time required for the process is acquired in advance and stored in the memory 41.例文帳に追加Then, the setting function 446 changes the tube voltage value from the first tube voltage value V1 to the second tube voltage within the allowable time based on the allowable time after control by the adjusting function 445 and the table stored in the memory 41. The first tube voltage value V1 and the second tube voltage value V2 are set so that they can be lowered to the value V2.

After the imaging conditions are set by the setting function 446, the system control function 441 executes imaging according to the set imaging conditions. For example, the system control function 441 generates X-rays by supplying a high voltage to the X-ray tube 11 according to set imaging conditions. Here, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 between the first tube voltage value V1 and the second tube voltage value V2, thereby viewing the X-ray energy. change each time. The system control function 441 also controls the bed drive device 32 to move the subject P into the imaging port of the gantry device 10 . Also, the system control function 441 adjusts the aperture and position of the collimator 17 . Also, the system control function 441 rotates the rotating portion by controlling the control device 15 .

Here, each detection element in the X-ray detector 12 detects X-rays that have passed through the subject P. FIG.
In addition, the plurality of DASs 18 included in the X-ray CT apparatus 1 sequentially collect X-ray signals for each detection element group. For example, the plurality of DASs 18 sequentially acquire X-ray signals from a detector element group consisting of the number of rows of detector elements adjusted by the adjustment function 445 .

For example, when the number of columns is adjusted to "n" by the adjustment function 445, each DAS 18 sequentially collects X-ray signals from a group of n detector elements from detector element 121 to detector element 12n. do. That is, when the number of columns is adjusted to "n", the plurality of DASs 18 provided in the X-ray CT apparatus 1 can detect from the entire area of the X-ray detector 12 (for example, the area indicated by the dot pattern in FIG. 17). , X-ray signals are acquired sequentially.

Further, for example, when the number of columns is adjusted to "m" by the adjustment function 445, each DAS 18 receives X-ray signals from the detection element group consisting of m detection elements from the detection element 121 to the detection element 12m. Collect sequentially. That is, when the number of columns is adjusted to "m", the plurality of DASs 18 provided in the X-ray CT apparatus 1 are partially arranged on the X-ray detector 12 (for example, the area indicated by the hatched pattern in FIG. 17). , the X-ray signals are collected sequentially.

A preprocessing function 442 preprocesses the detection data output from the DAS 18 . The generation function 443 also generates CT image data based on the preprocessed projection data, and utilizes the fact that X-ray absorption characteristics differ for each substance to identify the substance contained in the subject P. A process for discriminating types, atomic numbers, densities, etc. (hereinafter referred to as discrimination processing) is executed. Note that the discrimination process may be performed by an external device. For example, the output function 444 outputs projection data (detection data before preprocessing or raw data after preprocessing) to an external device connected to the X-ray CT apparatus 1 via a network. However, the external device may perform the discrimination processing. Also, the output function 444 outputs the CT image data generated by the generation function 443 and the results of the discrimination processing. For example, the output function 444 causes the display 42 to display a CT image for display based on CT image data and an image showing the result of discrimination processing on the CT image. Also, for example, the output function 444 outputs various data such as CT image data to an external device.

The case where the DAS 18 is connected to the n detection elements (the detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12 has been described so far. However, embodiments are not so limited. For example, when j detection elements (detection elements 221 to 22j) are arranged along the channel direction of the X-ray detector 12, the DAS 18 includes j detection elements from the detection element 221 to the detection element 22j. It may be connected to the sensing element. In this case, the X-ray CT apparatus 1 has the same number of DASs 18 as the number of columns in the X-ray detector 12, for example. Also, in this case, the adjustment function 445 adjusts, for example, the number of channels of the detection element group from which the DAS 18 collects signals.

For example, when the number of channels is adjusted to "j" by the adjustment function 445, each DAS 18 sequentially collects X-ray signals from a group of j detector elements from detector element 221 to detector element 22j. do. That is, when the number of columns is adjusted to "j", the plurality of DASs 18 provided in the X-ray CT apparatus 1 are arranged from the entire area of the X-ray detector 12 (for example, the area indicated by the dot pattern in FIG. 20) to X-ray signals are acquired sequentially. FIG. 20 is a diagram for explaining adjustment of the number of channels of the detection element group according to the fifth embodiment.

Also, for example, when the number of channels is adjusted to "k", which is less than "j", each DAS 18 sequentially acquires X-ray signals from a detection element group consisting of k detection elements. That is, when the number of columns is adjusted to "k", the plurality of DASs 18 provided in the X-ray CT apparatus 1 are arranged from a partial area of the X-ray detector 12 (for example, the area indicated by the hatched pattern in FIG. 20). , X-ray signals are acquired sequentially.

Also, until now, each DAS 18 has been used to sequentially collect X-ray signals from one row of detection elements in the X-ray detector 12, and each DAS 18 has received X-ray signals from one channel of detection elements in the X-ray detector 12. The case of sequentially acquiring line signals has been described. However, embodiments are not so limited. For example, each DAS 18 may sequentially collect X-ray signals from multiple rows of detection elements in the X-ray detector 12 . Further, for example, each DAS 18 may sequentially collect X-ray signals from the detection elements of a plurality of channels in the X-ray detector 12 . Alternatively, one DAS 18 may sequentially collect X-ray signals from all the detection elements in the X-ray detector 12 . Also, in this case, the adjustment function 445 may adjust both the number of columns and the number of channels of the detection element groups for which the DAS 18 collects signals.

Also, the case where the X-ray energy is changed for each view has been described so far. However, embodiments are not so limited. That is, the system control function 441 may change the X-ray energy for each of multiple views.

For example, the system control function 441 varies the X-ray energy for multiple views, as shown in FIG. Specifically, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T411 to time T412 to generate X-rays with energy E1. That is, the system control function 441 generates X-rays of energy E1 across the two views. FIG. 21 is a diagram showing an example of dual energy collection using the sequential collection DAS 18 according to the fifth embodiment.

Next, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the first tube voltage value V1 to the second tube voltage value V2. Here, when the number of columns of the detection element group for which the DAS 18 collects signals is "n", the allowable time for switching the tube voltage value supplied to the X-ray tube 11 is the period from time T413 to time T414. be. On the other hand, when the number of rows of the detection element group is adjusted to "m" by the adjustment function 445, the allowable time for switching the tube voltage value supplied to the X-ray tube 11 is the period from time T412 to time T414. be.

Next, the system control function 441 supplies the second tube voltage value V2 to the X-ray tube 11 at least from time T414 to time T415 to generate X-rays with energy E2. Next, the system control function 441 switches the tube voltage value supplied to the X-ray tube 11 from the second tube voltage value V2 to the first tube voltage value V1. Here, when the number of columns of the detection element group for which the DAS 18 collects signals is "n", the allowable time for switching the tube voltage value supplied to the X-ray tube 11 is the period from time T416 to time T417. be. On the other hand, when the number of rows of the detection element group is adjusted to "m" by the adjustment function 445, the allowable time for switching the tube voltage value supplied to the X-ray tube 11 is the period from time T415 to time T417. be. Next, the system control function 441 supplies the first tube voltage value V1 to the X-ray tube 11 at least from time T417 to time T418 to generate X-rays with energy E1.

As shown in FIG. 21, the adjustment function 445 reduces the number of columns of the detection element group for which the DAS 18 collects signals from 'n' to 'm', thereby increasing the voltage from the first tube voltage value V1 to the second tube voltage value V1. The allowable time for switching to the tube voltage value V2 is extended from "the period from time T413 to time T414" to "the period from time T412 to time T414". In addition, the adjustment function 445 reduces the number of columns of the detection element group from "n" to "m", so that the allowable time for switching from the second tube voltage value V2 to the first tube voltage value V1 is Extend from "the period from time T416 to time T417" to "the period from time T415 to time T417". That is, even when the system control function 441 changes the energy of the X-rays for each of a plurality of views, the adjustment function 445 adjusts the number of rows of the detection element groups for which the DAS 18 collects signals, thereby adjusting the X-ray tube. 11 can be controlled.

17 and 20, by changing the area on the X-ray detector 12 where X-ray signals are collected, the number of columns of detection element groups for which the DAS 18 collects signals and the case of adjusting at least one of the number of channels. However, embodiments are not so limited. For example, the adjustment function 445 may adjust at least one of the number of columns and the number of channels of the detection element groups for which the DAS 18 collects signals by adjusting bundling conditions when the DAS 18 collects signals. .

For example, when the DAS 18 is connected to n detection elements (detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12, the adjustment function 445 The bundling conditions are adjusted so that signals are bundled and collected for every two directionally adjacent detection elements. This allows the adjustment function 445 to substantially reduce the number of columns of detector elements from which the DAS 18 collects signals to "n/2".

Next, an example of the procedure of processing by the X-ray CT apparatus 1 will be described with reference to FIG. FIG. 22 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus 1 according to the fifth embodiment.

Step S<b>201 is a step corresponding to the adjustment function 445 . Step S<b>202 is a step corresponding to the setting function 446 . Steps S203 and S208 are steps corresponding to the system control function 441 . Step S<b>204 is a step corresponding to the preprocessing function 442 . Step S<b>205 is a step corresponding to the generation function 443 . Steps S206 and S207 are steps corresponding to the output function 444 .

First, the processing circuit 44 controls at least one of the number of columns and the number of channels of the detection element group for signal acquisition by the DAS 18, thereby controlling the permissible time for switching the tube voltage value supplied to the X-ray tube 11. (Step S201). Next, the processing circuit 44 sets imaging conditions such as a tube current value and a tube voltage value based on the allowable time after control (step S202).

Next, the processing circuit 44 causes the X-ray tube 11 to generate X-rays according to the imaging conditions set in step S202, and irradiates the subject P with the X-rays (step S203). At this time, the processing circuit 44 changes the X-ray energy for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . Also, the DAS 18 sequentially collects X-ray signals for each detection element group for which at least one of the number of columns and the number of channels has been adjusted in step S201, and generates detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 (step S204). The processing circuit 44 also generates CT image data based on the data (raw data) after preprocessing (step S205).

Here, the processing circuit 44 determines whether or not to display the CT image (step S206). If a CT image is to be displayed, such as when a display instruction is received from the operator (Yes at step S206), the processing circuit 44 generates a CT image for display based on the CT image data, and displays the generated CT image. The image is displayed on the display 42 (step S207). On the other hand, if the CT image is not to be displayed (No at step S206), or after step S207, the processing circuit 44 determines whether or not to end the imaging (step S208). If the image capturing is not to be finished, such as when there is an additional image capturing (No at step S208), the processing circuit 44 proceeds to step S201 again. On the other hand, if it is determined to end the shooting (Yes at step S208), the processing circuit 44 ends the process.

As described above, according to the fifth embodiment, the X-ray tube 11 generates X-rays. Also, the system control function 441 changes the energy of X-rays generated by the X-ray tube 11 for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . The X-ray detector 12 also has a plurality of detection elements that detect X-rays that have passed through the subject P. As shown in FIG. The DAS 18 also sequentially collects X-ray signals for each detection element group in the X-ray detector 12 . Further, the adjustment function 445 controls at least one of the number of columns and the number of channels of the detection element group for signal collection by the DAS 18, thereby controlling the permissible time for switching the tube voltage value supplied to the X-ray tube 11. . Therefore, the X-ray CT apparatus 1 according to the fifth embodiment can improve the degree of freedom of imaging conditions when performing dual energy acquisition by high-speed switching using the sequential acquisition system DAS 18 .

Also, as described above, according to the fifth embodiment, the setting function 446 sets the tube current value of the X-ray tube 11 based on the allowable time after control by the adjustment function 445 . For example, setting function 446 sets a lower tube current value based on the allowed time extended by adjustment function 445 . Therefore, the X-ray CT apparatus 1 according to the fifth embodiment can perform imaging under conditions of lower radiation exposure. Also, for example, the setting function 446 sets a higher tube current value based on the allowable time extended by the adjustment function 445 . Therefore, the X-ray CT apparatus 1 according to the fifth embodiment can perform imaging under conditions of higher image quality.

Also, as described above, according to the fifth embodiment, the setting function 446 sets the tube voltage value to be supplied to the X-ray tube 11 based on the allowable time after control by the adjustment function 445 . For example, the setting function 446 sets a combination with a larger voltage difference as the first tube voltage value and the second tube voltage value based on the allowable time extended by the adjustment function 445 . Therefore, the X-ray CT apparatus 1 according to the fifth embodiment can perform dual energy acquisition under conditions with a larger energy difference and improve the analysis performance of discrimination processing.

Note that the adjusting function 445 can improve the image quality of the CT image data reconstructed by the generating function 443 by reducing the number of rows of detection element groups for which the DAS 18 collects signals. That is, when the number of rows of the detector element group is small, the system control function 441 can perform imaging using X-rays with a small cone angle, thereby improving the image quality of reconstructed CT image data.

(Sixth embodiment)
In the fifth embodiment described above, a case has been described in which the imaging conditions are set based on the allowable time after control by the adjustment function 445 . On the other hand, in the sixth embodiment, a case will be described in which the permissible time is controlled based on the imaging conditions set by the setting function 446. FIG.

The X-ray CT apparatus 1 according to the sixth embodiment has the same configuration as the X-ray CT apparatus 1 shown in FIG. Hereinafter, the same reference numerals as those in FIG. 12 are assigned to the same configurations as those described in the fifth embodiment, and descriptions thereof are omitted.

First, the setting function 446 sets imaging conditions such as a tube current value and a tube voltage value. For example, the setting function 446 sets imaging conditions by receiving input operations of imaging conditions from the operator via the input interface 43 . Also, for example, the setting function 446 automatically sets imaging conditions based on positioning image data collected by positioning imaging. Also, for example, the setting function 446 sets preset conditions that are set in advance as imaging conditions.

For example, if information from dual energy collection is important, the setting function 446 sets a combination with a large voltage difference as the first tube voltage value and the second tube voltage value. Further, for example, when the exposure dose of the subject P is desired to be reduced, the setting function 446 sets the tube current value to a small value. Also, for example, when it is desired to acquire high-quality CT image data, the setting function 446 sets the tube current value to a large value.

Next, the adjustment function 445 adjusts at least one of the number of rows and the number of channels of the detection element group for collecting X-ray signals by the DAS 18 based on the imaging conditions set by the setting function 446, thereby Controls the allowable time for switching voltage values. In this embodiment, each of the plurality of DASs 18 is connected to n detection elements (detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12. A case will be described as an example.

For example, the setting function 446 sets the tube current value "700 mA", the first tube voltage value V1 "140 kV", and the second tube voltage value V2 "80 kV" as the imaging conditions. In this case, as shown in FIG. 18A, when the DAS 18 collects X-ray signals, the number of columns of the detection element group is "n". It is possible to increase from the voltage value V2 to the first tube voltage value V1. Further, as shown in FIG. 18A, it is also possible to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln. Therefore, in this case, the adjustment function 445 adjusts the number of columns of the detector element groups for which the DAS 18 collects the X-ray signals to "n".

Also, for example, the setting function 446 sets the tube current value “500 mA”, the first tube voltage value V1 “140 kV”, and the second tube voltage value V2 “80 kV” as imaging conditions. In this case, as shown in FIG. 18B, when the DAS 18 collects X-ray signals and the number of columns of the detection element group is "n", the tube voltage value is changed to the second tube voltage within the allowable time Ln. It is possible to increase from the voltage value V2 to the first tube voltage value V1.

However, as shown in FIG. 18B, when the tube current value is "500 mA", the tube voltage value can be decreased from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln. can't. Therefore, in this case, adjustment function 445 adjusts the number of columns of detector elements for which DAS 18 collects X-ray signals to a number smaller than "n". For example, the adjustment function 445 adjusts the number of columns of the detection element group in which the DAS 18 collects X-ray signals to "n/2".

Also, for example, the setting function 446 sets the tube current value “300 mA”, the first tube voltage value V1 “140 kV”, and the second tube voltage value V2 “80 kV” as imaging conditions. In this case, as shown in FIG. 18C, the tube voltage value is changed to the second tube voltage within the allowable time Ln when "n" is the number of columns of the detection element group for collecting X-ray signals by the DAS 18. It is possible to increase from the voltage value V2 to the first tube voltage value V1.

However, as shown in FIG. 18C, when the tube current value is "300 mA", the tube voltage value can be lowered from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln. can't. Further, when the tube current value is "300 mA", in order to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2, it takes a longer time than when the tube current value is "500 mA". It takes time. Therefore, in this case, the adjustment function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects X-ray signals to a number smaller than "n/2". For example, the adjustment function 445 adjusts the number of columns of the detection element group in which the DAS 18 collects X-ray signals to "n/4".

Also, for example, the setting function 446 sets the tube current value “500 mA”, the first tube voltage value V1 “150 kV”, and the second tube voltage value V2 “70 kV” as imaging conditions. In this case, as shown in FIG. 19A, when the DAS 18 collects X-ray signals, the number of columns of the detection element group is "n". It is possible to increase from the voltage value V2 to the first tube voltage value V1.

However, as shown in FIG. 19A, when the tube voltage value V1 is "150 kV" and the second tube voltage value V2 is "70 kV", the tube voltage value is changed from the first tube voltage value V1 within the allowable time Ln. It cannot be lowered to the second tube voltage value V2. Therefore, in this case, adjustment function 445 adjusts the number of columns of detector elements for which DAS 18 collects X-ray signals to a number smaller than "n". For example, the adjustment function 445 adjusts the number of columns of the detection element group in which the DAS 18 collects X-ray signals to "n/2".

Also, for example, the setting function 446 sets the tube current value “500 mA”, the first tube voltage value V1 “160 kV”, and the second tube voltage value V2 “60 kV” as imaging conditions. In this case, as shown in FIG. 19B, the tube voltage value is changed to the second tube voltage value within the allowable time Ln when "n" is the number of columns of the detection element group for collecting X-ray signals by the DAS 18. It is possible to increase from the voltage value V2 to the first tube voltage value V1.

However, as shown in FIG. 19B, when the tube voltage value V1 is "160 kV" and the second tube voltage value V2 is "60 kV", the tube voltage value is changed from the first tube voltage value V1 within the allowable time Ln. It cannot be lowered to the second tube voltage value V2. Further, in order to change the tube voltage value when the voltage difference between the first tube voltage value V1 and the second tube voltage value V2 is "100 kV", a longer time than when the voltage difference is "80 kV" is required. requires. Therefore, in this case, the adjustment function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects X-ray signals to a number smaller than "n/2". For example, the adjustment function 445 adjusts the number of columns of the detection element group in which the DAS 18 collects X-ray signals to "n/4".

As described above, the adjustment function 445 can adjust the number of rows of the detection element group for the DAS 18 to acquire X-ray signals based on the imaging conditions set by the setting function 446 . For example, the adjustment function 445 compares the imaging conditions set by the setting function 446 with a table that defines the correspondence relationship between the imaging conditions and the number of rows of the detection element group, thereby determining the number of rows of the detection element group. to adjust.

For example, the adjustment function 445 first acquires in advance the table shown in FIG. The vertical axis of the table shown in FIG. 23 indicates the kV difference (voltage difference), and the horizontal axis indicates the tube current value. Further, when the imaging conditions are set by the setting function 446, the adjustment function 445 reads the table from the memory 41 and compares it with the set imaging conditions. Thereby, the adjustment function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects X-ray signals. Note that FIG. 23 is a diagram for explaining an example of the allowable time control according to the sixth embodiment.

For example, when the tube current value “700 mA”, the first tube voltage value V1 “140 kV”, and the second tube voltage value V2 “80 kV” are set as the imaging conditions, the adjustment function 445 first sets the voltage Calculate the difference "60 kV". Next, the adjusting function 445 acquires the number of columns "n" by referring to the table in FIG. 23 for the tube current value "700 mA" and the voltage difference "60 kV". Then, the adjustment function 445 adjusts the number of rows of the detection element group for which the DAS 18 acquires X-ray signals according to the acquired number of rows “n”, and controls the allowable time.

Similarly, when the tube current value is "700 mA" and the voltage difference is "80 kV", the adjustment function 445 acquires the number of columns "n/2" based on the table in FIG. Also, when the tube current value is "700 mA" and the voltage difference is "100 kV", the adjustment function 445 acquires the number of columns "n/2" based on the table in FIG. Also, when the tube current value is "500 mA" and the voltage difference is "60 kV", the adjusting function 445 acquires the number of columns "n/2" based on the table in FIG. Also, when the tube current value is "500 mA" and the voltage difference is "80 kV", the adjustment function 445 acquires the number of columns "n/2" based on the table in FIG. Also, when the tube current value is "500 mA" and the voltage difference is "100 kV", the adjustment function 445 acquires the number of columns "n/4" based on the table in FIG. Also, when the tube current value is "300 mA" and the voltage difference is "60 kV", the adjustment function 445 acquires the number of columns "n/4" based on the table in FIG. Also, when the tube current value is "300 mA" and the voltage difference is "80 kV", the adjustment function 445 acquires the number of columns "n/4" based on the table in FIG. Also, when the tube current value is "300 mA" and the voltage difference is "100 kV", the adjusting function 445 acquires the number of columns "n/4" based on the table in FIG. Then, the adjustment function 445 adjusts the number of rows of the detection element group for which the DAS 18 collects X-ray signals according to the acquired number of rows, and controls the allowable time.

To give another example, the adjustment function 445 calculates the number of rows of the detection element group from the imaging conditions set by the setting function 446 . For example, the adjustment function 445 first adjusts the first tube voltage value V1 to the second tube voltage value based on the set tube current value, first tube voltage value V1, and second tube voltage value V2. Calculate the time required to decrease the tube voltage value to V2. Then, the adjustment function 445 adjusts the DAS 18 to adjust the X-ray signal so that the allowable time is longer than the time required to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2. Adjust the number of columns of the detection element group for acquisition. For example, the adjustment function 445 allows the DAS 18 to adjust the X-ray signal within a range in which the allowable time is longer than the time required to decrease the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2. Maximize the number of rows of detector elements that collect.

Next, an example of the procedure of processing by the X-ray CT apparatus 1 will be described with reference to FIG. FIG. 24 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus 1 according to the sixth embodiment.

Step S<b>301 is a step corresponding to the setting function 446 . Step S302 is a step corresponding to the adjustment function 445. FIG. Steps S303 and S308 are steps corresponding to the system control function 441 . Step S<b>304 is a step corresponding to the preprocessing function 442 . Step S<b>305 is a step corresponding to the generation function 443 . Steps S306 and S307 are steps corresponding to the output function 444 .

First, the processing circuit 44 sets imaging conditions (step S301). For example, the processing circuit 44 sets imaging conditions desired by the operator by receiving input operations of imaging conditions from the operator via the input interface 43 . Next, the processing circuit 44 adjusts at least one of the number of columns and the number of channels of the detection element group from which the DAS 18 collects signals based on the set imaging conditions, thereby adjusting the tube voltage supplied to the X-ray tube 11. The permissible time for value switching is controlled (step S302).

Next, the processing circuit 44 causes the X-ray tube 11 to generate X-rays according to the imaging conditions set in step S301, and irradiates the subject P with the X-rays (step S303). At this time, the processing circuit 44 changes the X-ray energy for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . In addition, the DAS 18 sequentially acquires X-ray signals for each detection element group for which at least one of the number of columns and the number of channels is adjusted in step S302, and generates detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 (step S304). The processing circuit 44 also generates CT image data based on the data (raw data) after preprocessing (step S305).

Here, the processing circuit 44 determines whether or not to display the CT image (step S306). If a CT image is to be displayed, such as when a display instruction is received from the operator (Yes at step S306), the processing circuit 44 generates a CT image for display based on the CT image data, and The image is displayed on the display 42 (step S307). On the other hand, if the CT image is not to be displayed (No at step S306), or after step S307, the processing circuit 44 determines whether or not to end the imaging (step S308). If the image capturing is not to be finished, such as when there is an additional image capturing (No at step S308), the processing circuit 44 proceeds to step S301 again. On the other hand, if it is determined to end the shooting (Yes at step S308), the processing circuit 44 ends the process.

As described above, the setting function 446 according to the sixth embodiment sets shooting conditions. In addition, the adjustment function 445 adjusts at least one of the number of columns and the number of channels of the detection element group for collecting X-ray signals by the DAS 18 based on the imaging conditions set by the setting function 446, so that the allowable time to control. Therefore, the X-ray CT apparatus 1 according to the sixth embodiment can improve the degree of freedom of imaging conditions when performing dual energy acquisition by high-speed switching using the DAS 18 of the sequential acquisition system. That is, the X-ray CT apparatus 1 can improve the degree of freedom of the imaging conditions by setting the imaging conditions first while performing control so that the switching of the tube voltage value is completed within the allowable time. .

(Seventh embodiment)
In the fifth embodiment described above, a case has been described in which the imaging conditions are set based on the allowable time after control by the adjustment function 445 . On the other hand, in the seventh embodiment, a case will be described in which shooting conditions are set in consideration of not only the allowable time but also the shooting time.

The X-ray CT apparatus 1 according to the seventh embodiment has the same configuration as the X-ray CT apparatus 1 shown in FIG. Hereinafter, the same reference numerals as those in FIG. 12 are assigned to the same configurations as those described in the fifth embodiment, and descriptions thereof are omitted. In this embodiment, each of the plurality of DASs 18 is connected to n detection elements (detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12. A case will be described as an example.

First, the adjustment function 445 acquires an imaging range in which the subject P is imaged. For example, the adjusting function 445 acquires the imaging range by receiving an input operation of the imaging range from the operator via the input interface 43 . Also, for example, the adjustment function 445 automatically acquires the imaging range based on positioning image data collected by positioning imaging. Also, for example, the adjustment function 445 automatically acquires the imaging range from a system such as RIS (Radiology Information System) or HIS (Hospital Information System) via a network. For example, the adjustment function 445 acquires the length of the subject P in the body axis direction as the imaging range.

Further, the adjustment function 445 acquires a predetermined imaging time for imaging the subject P. FIG. Here, the predetermined imaging time is, for example, the upper limit of the imaging time that can be set for imaging the subject P. For example, when imaging the chest or abdomen of the subject P, the subject P holds his/her breath until the imaging is completed. In this case, the adjustment function 445 acquires the breath-holding time of the subject P as the predetermined imaging time.

For example, the adjusting function 445 acquires the breath-holding time by receiving an input operation of the breath-holding time according to the subject P from the operator. Also, for example, the adjustment function 445 acquires a preset value set in advance as the breath-holdable time. In addition, for example, the adjustment function 445 acquires patient information (medical condition, age, physique, etc.) of the subject P from a system such as RIS or HIS, and sets the allowable breath-holding time of the subject P based on the patient information. . For example, the adjustment function 445 sets the allowable breath-hold time to “5 seconds” if the subject P has a lung disease, and sets the allowable breath-hold time to “5 seconds” if the subject P does not have a lung disease. Set to "10 seconds".

Next, the adjusting function 445 adjusts at least one of the number of columns and the number of channels of the detection element group for signal collection by the DAS 18 so that imaging is completed within a predetermined imaging time based on the imaging range. In the following, as an example, as shown in FIG. 25, a case where the imaging range is "500 mm" and the predetermined imaging time is "10 seconds" will be described. Note that FIG. 25 is a diagram for explaining an example of the allowable time control according to the seventh embodiment.

For example, the adjustment function 445 receives an operation to set the range A shown in FIG. 26 from the operator who referred to the positioning image data, and acquires the length of range A "500 mm" as the imaging range. In addition, since the range A includes the chest, the adjustment function 445 acquires the breath-holdable time of the subject P as the predetermined imaging time. Note that FIG. 26 is a diagram for explaining an example of the allowable time control according to the seventh embodiment.

Next, the adjustment function 445 calculates an imaging time according to the number of rows of the detection element group for which the DAS 18 collects signals based on the imaging range. For example, as shown in FIG. 25, the adjusting function 445 calculates the shooting time "6.25 seconds" according to the number of columns "n" based on the shooting range "500 mm". Also, for example, the adjustment function 445 calculates the shooting time “12.5 seconds” corresponding to the number of columns “n/2” based on the shooting range “500 mm”. Also, for example, the adjustment function 445 calculates the shooting time “25 seconds” according to the number of columns “n/4” based on the shooting range “500 mm”.

For example, the adjustment function 445 first calculates the width of the imaging target region in the subject P in the column direction according to the number of columns of the detection element group. Next, the adjusting function 445 moves the subject P with respect to the gantry 10 while the rotating part of the X-ray CT apparatus 1 rotates once based on the width of the imaging target region in the column direction and the beam pitch. Calculate quantity. The beam pitch is a setting value indicating the ratio between the amount of movement of the subject P with respect to the gantry 10 during one rotation of the rotating section and the width of the imaging target region of the subject P in the column direction. . Next, the adjustment function 445 divides the imaging range by the product of the amount of movement of the subject P with respect to the gantry 10 during one rotation of the rotating part and the rotation speed of the rotating part, thereby obtaining the detection element The imaging time is calculated according to the number of columns in the group.

Next, the adjustment function 445 compares the imaging time corresponding to the number of columns with a predetermined imaging time, and identifies the number of columns for which the imaging time corresponding to the number of columns is shorter than the predetermined imaging time. Note that hereinafter, the number of columns for which the imaging time corresponding to the number of columns is shorter than the predetermined imaging time is referred to as a candidate for the number of columns. That is, the adjustment function 445 identifies candidates for the number of columns by comparing the shooting time according to the number of columns with a predetermined shooting time.

For example, in FIG. 25, the imaging time corresponding to the number of columns "n/2" is "12.5 seconds", and the imaging time corresponding to the number of columns "n/4" is "25 seconds". That is, the shooting time corresponding to the number of columns "n/2" and the shooting time corresponding to the number of columns "n/4" exceed the predetermined shooting time "10 seconds". In other words, when the number of rows of the detection element group is "n/2" or "n/4", it takes longer than the predetermined imaging time of "10 seconds" to complete the imaging. Therefore, the adjustment function 445 does not identify "n/2" and "n/4" as candidates for the number of columns.

Also, in FIG. 25, the shooting time corresponding to the number of columns "n" is "6.25 seconds". That is, the shooting time corresponding to the number of columns "n" is shorter than the predetermined shooting time "10 seconds". In other words, when the number of rows of the detection element group is "n", the imaging can be completed within the predetermined imaging time of "10 seconds". Therefore, the adjustment function 445 identifies "n" as a candidate for the number of columns.

Note that if there is one candidate for the number of columns, the adjustment function 445 adjusts the number of columns of the detection element group from which the DAS 18 collects signals according to the candidate for the number of columns. For example, in the case shown in FIG. 25, adjustment function 445 adjusts the number of columns of detector elements from which DAS 18 collects signals to "n". If there are multiple candidates for the number of columns, the adjustment function 445 accepts an operation to select one of the candidates from the operator, and according to the selected candidate for the number of columns, the detection element group for which the DAS 18 collects signals. Adjust the number of columns.

As described above, the adjustment function 445 calculates the shooting time corresponding to the number of columns based on the shooting range. In addition, the adjustment function 445 identifies the number of columns for which the shooting time corresponding to the number of columns is shorter than the predetermined shooting time as candidates for the number of columns. Further, the adjusting function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects signals based on the candidate for the number of columns. That is, the adjusting function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects signals so that the imaging is completed within a predetermined imaging time. In addition, the adjustment function 445 controls the allowable time for switching the tube voltage value supplied to the X-ray tube 11 when executing dual energy acquisition by high-speed switching by adjusting the number of rows of the detection element group.

In the case shown in FIG. 25, when the predetermined imaging time is "5 seconds", the number of columns of the detection element group is set to "n", and the number of columns of the detection element group is set to "n/2". ” and the case where the number of columns of the detection element group is set to “n/4”, the imaging time corresponding to the number of columns exceeds the predetermined imaging time of “10 seconds”. In other words, the adjustment function 445 may not be able to identify candidates for the number of columns.

In this case, the adjustment function 445 adjusts the shooting pitch, for example. Here, the imaging pitch is, for example, a beam pitch or a helical pitch. The beam pitch is the ratio of the amount of movement of the subject P with respect to the gantry 10 during one rotation of the rotating part of the X-ray CT apparatus 1 to the width of the imaging target region of the subject P in the column direction. is. The helical pitch corresponds to the amount of movement of the subject P with respect to the gantry 10 during one rotation of the rotating part of the X-ray CT apparatus 1, and to one row of detection elements in the imaging target area of the subject P. It is the ratio to the width (collimation width). The amount of movement of the subject P with respect to the gantry 10 during one rotation of the rotating portion of the X-ray CT apparatus 1 is adjusted, for example, by the movement speed of the tabletop 33 during imaging. In this embodiment, a case of adjusting the beam pitch will be described as an example.

For example, if no candidates for the number of rows can be identified, the adjustment function 445 adjusts the moving speed of the table top so as to increase the beam pitch. Further, the adjusting function 445 recalculates the imaging time corresponding to the number of columns based on the adjusted beam pitch. Here, due to the increase in beam pitch, the adjustment function 445 recalculates a shorter imaging time according to the number of columns.

For example, the adjustment function 445 calculates a time shorter than "6.25 seconds" as the imaging time corresponding to the number of columns "n". Also, the adjustment function 445 calculates a time shorter than "12.5 seconds" as the imaging time according to the number of columns "n/2". Also, the adjustment function 445 calculates a time shorter than "25 seconds" as the imaging time according to the number of columns "n/4". As a result, the adjustment function 445 identifies at least one candidate for the number of columns even when the predetermined imaging time is "5 seconds", and adjusts the number of columns of the detection element group for which the DAS 18 collects signals. can do. That is, the adjustment function 445 adjusts the number of rows of the detection element group for signal collection by the DAS 18 and the pitch of imaging so that imaging is completed within a predetermined imaging time.

Furthermore, the setting function 446 sets the imaging conditions based on the allowable time after control by the adjustment function 445 . For example, the setting function 446 sets the tube voltage value from the first tube voltage value V1 to the second tube voltage value V2 for each combination of the tube current value, the first tube voltage value V1 and the second tube voltage value V2. A table defining the time required for lowering is obtained in advance and stored in the memory 41.例文帳に追加Then, the setting function 446 sets the tube current value, the first tube voltage value V1 and the second tube voltage value V2 based on the allowable time after the control by the adjustment function 445 and the table stored in the memory 41. do. Specifically, the setting function 446 sets the tube voltage value supplied to the X-ray tube 11 between the first tube voltage value V1 and the second tube voltage value V2 within the allowable time after the control by the adjustment function 445. The tube current value, the first tube voltage value V1 and the second tube voltage value V2 are set so as to be switchable between them.

For example, as shown in FIGS. 18B and 18C, when the first tube voltage value V1 is "140 kV" and the second tube voltage value V2 is "80 kV", the tube current value is set to "500 mA". Alternatively, when set to "300 mA", the tube voltage value is decreased from the first tube voltage value V1 to the second tube voltage value V2 within the allowable time Ln when the number of rows of the detection element group is "n". I can't let you. On the other hand, as shown in FIG. 18A, when the tube current value is set to "700 mA", the tube voltage value is changed from the first tube voltage value V1 to the second tube voltage value within the allowable time Ln. It is possible to go down to V2. Therefore, the setting function 446 sets "700 mA" as the tube current value of the X-ray tube when the number of rows of the detection element group is adjusted to "n".

In the above description, the case where the length of range A shown in FIG. Similarly, the number of columns of the detection element group can be adjusted.

For example, the adjustment function 445 receives an operation of setting range B shown in FIG. 26 from the operator who referred to the positioning image data, and acquires the length of range B "300 mm" as the imaging range. Here, as shown in FIG. 27, the adjustment function 445 is based on the imaging range of "300 mm", and the DAS 18 collects signals so that imaging is completed in a predetermined imaging time of "10 seconds". number of columns to "n/2". Note that FIG. 27 is a diagram for explaining an example of the allowable time control according to the seventh embodiment.

Note that when the imaging range is "300 mm", the imaging time corresponding to the number of columns "n" is "3.75 seconds" which is half of "7.5 seconds". That is, when the imaging range is "300 mm", there are two row numbers (candidates for row numbers) where the imaging time corresponding to the row number is shorter than the predetermined imaging time, "n" and "n/2". . In this case, the adjustment function 445 receives an operation of selecting one of the candidates from the operator. For example, the operator selects "n/2" when giving priority to the degree of freedom of imaging conditions. Also, the operator selects "n" when giving priority to shortening the imaging time. Note that FIG. 27 shows a case where "n/2" is selected from two candidates for the number of columns.

Also, for example, the adjustment function 445 receives an operation to set a range C shown in FIG. 26 from the operator who referred to the positioning image data, and acquires the length of range C "200 mm" as the imaging range. Here, as shown in FIG. 27, the adjustment function 445 is based on the imaging range of 200 mm, and the DAS 18 collects signals so that imaging is completed in a predetermined imaging time of 10 seconds. number of columns to "n/4".

When the shooting range is "200 mm", the shooting time corresponding to the number of columns "n/2" is "5 seconds" which is half of "10 seconds", and the shooting time corresponding to the number of columns "n" is " 1/4 of "10 seconds" is "2.5 seconds". That is, when the imaging range is "200 mm", the number of columns (candidates for the number of columns) for which the imaging time corresponding to the number of columns is shorter than the predetermined imaging time is "n", "n/2", and "n/4". ” exists. Therefore, the adjustment function 445 receives an operation of selecting one of the candidates from the operator. Note that FIG. 27 shows a case where "n/4" is selected among the three candidates for the number of columns.

Next, an example of the procedure of processing by the X-ray CT apparatus 1 according to the seventh embodiment will be described with reference to FIG. FIG. 28 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus 1 according to the seventh embodiment.

Steps S401 , S402 , S403 , S404 , S405 , S406 , S407 and S408 are steps corresponding to the adjustment function 445 . Step S409 is a step corresponding to the setting function 446. FIG. Steps S410 and S415 are steps corresponding to the system control function 441 . Step S<b>411 is a step corresponding to the preprocessing function 442 . Step S<b>412 is a step corresponding to the generation function 443 . Steps S413 and S414 are steps corresponding to the output function 444 .

First, the processing circuit 44 acquires a predetermined photographing time (step S401). Also, the processing circuit 44 acquires the imaging range (step S402). Next, the processing circuit 44 calculates the imaging time according to the number of columns of the detection element group from which the DAS 18 collects signals based on the imaging range (step S403). For example, the processing circuit 44 calculates the photographing time required to complete the photographing of the photographing range for each of the numbers of columns "n", "n/2" and "n/4".

Here, the processing circuit 44 determines whether or not candidates for the number of columns have been specified based on the predetermined shooting time and the shooting time corresponding to the number of columns (step S404). If no candidate for the number of columns is identified (No at step S404), the processing circuitry 44 adjusts the beam pitch (step S405), and proceeds to step S403 again.

On the other hand, if at least one candidate for the number of columns is specified (Yes at step S404), the processing circuitry 44 determines whether there are a plurality of candidates for the number of columns (step S406). Here, if there are a plurality of candidates for the number of columns (Yes at step S406), the processing circuit 44 receives an operation of selecting one of the candidates for the number of columns from the operator (step S407).

On the other hand, when there are not a plurality of candidates for the number of columns, such as when the number of columns that can complete the imaging of the imaging range in the predetermined imaging time is only "n" (No in step S406), or after step S407 , the processing circuit 44 controls the permissible time for switching the tube voltage value supplied to the X-ray tube 11 by adjusting the number of rows of the detection element groups for which the DAS 18 collects signals (step S408). The processing circuit 44 also sets imaging conditions such as the tube current value and the tube voltage value based on the allowable time after control (step S409).

Next, the processing circuit 44 causes the X-ray tube 11 to generate X-rays according to the imaging conditions set in step S409, and irradiates the subject P with the X-rays (step S410). At this time, the processing circuit 44 changes the X-ray energy for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . In addition, the DAS 18 sequentially collects X-ray signals for each detection element group whose number of columns has been adjusted in step S408 to generate detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 (step S411). The processing circuit 44 also generates CT image data based on the data (raw data) after preprocessing (step S412).

Here, processing circuit 44 determines whether or not to display a CT image (step S413). If a CT image is to be displayed, such as when a display instruction is received from the operator (Yes at step S413), the processing circuit 44 generates a CT image for display based on the CT image data, and displays the generated CT image. The image is displayed on the display 42 (step S414). On the other hand, if the CT image is not to be displayed (No at step S413), or after step S414, the processing circuit 44 determines whether or not to end the imaging (step S415). If the image capturing is not to be finished, such as when there is an additional image capturing (No at step S415), the processing circuit 44 proceeds to step S402 again. On the other hand, if it is determined to end the shooting (Yes at step S415), the processing circuit 44 ends the process.

It should be noted that if the photographing is not to be ended (No at step S415), the processing circuit 44 may proceed to step S401. That is, the processing circuitry 44 may acquire a predetermined imaging time for each imaging. Also, in this case, step S401 can be performed at any timing before step S404.

As described above, the adjustment function 445 according to the seventh embodiment adjusts the number of columns of the detection element groups for which the DAS 18 collects signals based on the imaging range so that imaging is completed within a predetermined imaging time. do. Specifically, the adjustment function 445 calculates the imaging time corresponding to the number of columns based on the imaging range, and specifies the number of columns in which the imaging time corresponding to the number of columns is shorter than the predetermined imaging time as candidates for the number of columns. Then, based on the candidate for the number of columns, the DAS 18 adjusts the number of columns of the detection element group for signal collection. Therefore, the X-ray CT apparatus 1 according to the seventh embodiment improves the degree of freedom of imaging conditions, performs control so that the switching of the tube voltage value is completed within the allowable time, and furthermore, can be performed within a predetermined imaging time. You can complete the shooting.

Further, as described above, the adjusting function 445 adjusts the shooting pitch when the number of rows (candidate for the number of rows) capable of completing shooting of the shooting range in a predetermined shooting time cannot be specified. That is, the adjustment function 445 adjusts the number of rows of the detection element group for signal collection by the DAS 18 and the pitch of imaging so that imaging is completed within a predetermined imaging time. Therefore, the X-ray CT apparatus 1 according to the seventh embodiment can complete imaging within a predetermined imaging time by adjusting the imaging pitch even when the imaging range is wide.

(Eighth embodiment)
In the sixth embodiment described above, based on the imaging conditions set by the setting function 446, the DAS 18 adjusts at least one of the number of columns and the number of channels of the detection element group for collecting X-ray signals, A case of controlling the allowable time has been described. On the other hand, in the eighth embodiment, a case will be described in which the permissible time is controlled in consideration of not only the photographing conditions but also the photographing time.

The X-ray CT apparatus 1 according to the eighth embodiment has the same configuration as the X-ray CT apparatus 1 shown in FIG. Hereinafter, the same reference numerals as those in FIG. 12 are assigned to the same configurations as those described in the fifth embodiment, and descriptions thereof are omitted. In this embodiment, each of the plurality of DASs 18 is connected to n detection elements (detection elements 121 to 12n) arranged along the column direction of the X-ray detector 12. A case will be described as an example.

First, the adjustment function 445 acquires an imaging range in which the subject P is imaged. For example, the adjusting function 445 acquires the imaging range by receiving an input operation of the imaging range from the operator via the input interface 43 . Also, for example, the adjustment function 445 automatically acquires the imaging range based on positioning image data collected by positioning imaging. Also, for example, the adjustment function 445 automatically acquires the imaging range from a system such as RIS or HIS via a network. As an example, a case where the imaging range is "500 mm" as shown in FIG. 29 will be described below. FIG. 29 is a diagram for explaining an example of allowable time control according to the eighth embodiment.

Further, the adjustment function 445 acquires a predetermined imaging time for imaging the subject P. FIG. For example, the adjustment function 445 acquires a predetermined imaging time by receiving an input operation of a breath-holding possible time corresponding to the subject P from the operator. Also, for example, the adjustment function 445 acquires a preset value that is set in advance as the predetermined shooting time. Also, for example, the adjustment function 445 acquires the breath-holdable time of the subject P based on the patient information as the predetermined imaging time. In the following, as an example, as shown in FIG. 29, a case where the predetermined imaging time is "10 seconds" will be described.

A setting function 446 sets imaging conditions such as a tube current value and a tube voltage value. For example, the setting function 446 sets imaging conditions by receiving input operations of imaging conditions from the operator via the input interface 43 . Also, for example, the setting function 446 automatically sets imaging conditions based on positioning image data collected by positioning imaging. Also, for example, the setting function 446 sets preset conditions that are set in advance as imaging conditions. In the following, as an example, as shown in FIG. 29, the case where the tube current value "500 mA", the first tube voltage value V1 "140 kV", and the second tube voltage value V2 "80 kV" are set as the imaging conditions. explain.

Next, the adjustment function 445 identifies the number of columns that can be selected based on the shooting conditions set by the setting function 446 . For example, the adjustment function 445 first sets the permissible time when the number of columns of the detection element group for collecting X-ray signals by the DAS 18 is "n", and the number of columns of the detection element group is "n/2". , and the allowable time when the number of columns of the detection element group is "n/4". Such allowable time is, for example, measured in advance and stored in the memory 41 in association with the number of columns of the detection element group. Next, the adjustment function 445 can switch the tube voltage value between the first tube voltage value V1 and the second tube voltage value V2 within the allowable time for each of the acquired plurality of allowable times. It is determined whether or not.

Below, the tube voltage value is set between the first tube voltage value V1 “140 kV” and the second tube voltage value V2 “80 kV” within the allowable time when the number of columns of the detection element group is “n”. It is assumed that it is possible to switch with Further, in the following description, the tube voltage value is changed to the first tube voltage value V1 of 140 kV and the second tube voltage value V2 of 80 kV within the allowable time when the number of columns of the detection element group is set to "n/2". ” shall be possible to switch between. Further, in the following description, the tube voltage value is changed from the first tube voltage value V1 of "140 kV" to the second tube voltage value V2 of "80 kV" within the allowable time when the number of columns of the detection element group is "n/4". ” shall not be possible to switch between In this case, the adjustment function 445 identifies "n" and "n/2" as the number of selectable columns, as shown in FIG.

Next, the adjustment function 445 calculates the imaging time according to the number of columns of the detection element group from which the DAS 18 collects signals, based on the selectable number of columns and imaging range. For example, as shown in FIG. 29, the adjustment function 445 sets the imaging time "6.25 seconds" according to the number of rows "n" based on the number of rows "n" that can be selected and the imaging range "500 mm". calculate. Further, the adjustment function 445 calculates the shooting time "12.5 seconds" corresponding to the number of rows "n/2" based on the number of rows "n/2" and the shooting range "500 mm" that can be selected.

Next, the adjustment function 445 identifies candidates for the number of columns by comparing the shooting time corresponding to the number of columns with a predetermined shooting time. For example, in FIG. 29, the shooting time corresponding to the number of columns "n/2" is "12.5 seconds". That is, the shooting time corresponding to the number of columns "n/2" exceeds the predetermined shooting time "10 seconds". Therefore, the adjustment function 445 does not identify the number of columns "n/2" as a candidate for the number of columns.

Also, in FIG. 29, the imaging time corresponding to the number of columns "n" is "6.25 seconds". That is, the shooting time corresponding to the number of columns "n" is shorter than the predetermined shooting time "10 seconds". Therefore, the adjustment function 445 identifies the number of columns "n" as a candidate for the number of columns. Note that if there is one candidate for the number of columns, the adjustment function 445 adjusts the number of columns of the detection element group from which the DAS 18 collects signals according to the candidate for the number of columns. If there are multiple candidates for the number of rows, the adjustment function 445 receives an operation to select one of the candidates from the operator, and adjusts the number of rows of the detection element group according to the selected candidate for the number of rows.

As described above, the adjustment function 445 identifies candidates for the number of columns based on the predetermined imaging time, and adjusts the number of columns of detector elements from which the DAS 18 collects signals. That is, the adjusting function 445 adjusts the number of columns of the detection element group for which the DAS 18 collects signals so that the imaging is completed within a predetermined imaging time. In addition, the adjustment function 445 controls the allowable time for switching the tube voltage value supplied to the X-ray tube 11 when executing dual energy acquisition by high-speed switching by adjusting the number of rows of the detection element group.

In the case shown in FIG. 29, when the predetermined imaging time is "5 seconds", the number of columns of the detection element group is set to "n" and the number of columns of the detection element group is set to "n/2". , the imaging time corresponding to the number of columns exceeds the predetermined imaging time of "10 seconds". In other words, the adjustment function 445 may not be able to identify candidates for the number of columns. In this case, the adjusting function 445 adjusts the shooting pitch (beam pitch, helical pitch, etc.). In addition, in this embodiment, the case of adjusting the beam pitch will be described as an example.

For example, if no candidates for the number of rows can be identified, the adjustment function 445 adjusts the moving speed of the table top so as to increase the beam pitch. Further, the adjusting function 445 recalculates the imaging time corresponding to the number of columns based on the adjusted beam pitch. Here, due to the increase in beam pitch, the adjustment function 445 recalculates a shorter imaging time according to the number of columns.

For example, the adjustment function 445 calculates a time shorter than "6.25 seconds" as the imaging time corresponding to the number of columns "n". Also, the adjustment function 445 calculates a time shorter than "12.5 seconds" as the imaging time according to the number of columns "n/2". As a result, the adjustment function 445 identifies at least one candidate for the number of columns even when the predetermined imaging time is "5 seconds", and adjusts the number of columns of the detection element group for which the DAS 18 collects signals. can do. That is, the adjustment function 445 adjusts the number of rows of the detection element group for signal collection by the DAS 18 and the pitch of imaging so that imaging is completed within a predetermined imaging time.

It should be noted that increasing the beam pitch may degrade the quality of the acquired CT image data. Therefore, when the image quality of CT image data is important, the adjustment function 445 may avoid an increase in beam pitch by changing imaging conditions. On the other hand, when the set imaging conditions are important, such as when information from dual energy acquisition is important, or when low radiation exposure is important for imaging, the adjustment function 445 increases the beam pitch by , to maintain the shooting conditions.

Next, an example of the procedure of processing by the X-ray CT apparatus 1 according to the eighth embodiment will be described with reference to FIG. FIG. 30 is a flowchart for explaining a series of processing flows of the X-ray CT apparatus 1 according to the eighth embodiment.

Steps S 501 , S 502 , S 504 , S 505 , S 506 , S 507 , S 508 , S 509 and S 510 are steps corresponding to adjustment function 445 . Step S<b>503 is a step corresponding to the setting function 446 . Steps S511 and S516 are steps corresponding to the system control function 441 . Step S512 is a step corresponding to the preprocessing function 442. FIG. Step S<b>513 is a step corresponding to the generation function 443 . Steps S514 and S515 are steps corresponding to the output function 444 .

First, the processing circuit 44 acquires a predetermined photographing time (step S501). Also, the processing circuit 44 acquires the imaging range (step S502). Note that step S502 can be performed at any timing before step S505. Further, the processing circuit 44 sets imaging conditions (step S503). For example, the processing circuit 44 sets imaging conditions desired by the operator by receiving input operations of imaging conditions from the operator via the input interface 43 .

The processing circuit 44 also identifies the number of selectable columns based on the imaging conditions acquired in step S503 (step S504). For example, the processing circuit 44 identifies the number of columns "n" and "n/2" as the numbers of selectable columns based on whether the tube voltage value can be switched within the allowable time.

Further, the processing circuit 44 calculates the imaging time according to the number of columns for each of the identified numbers of columns based on the imaging range acquired in step S502 (step S505). For example, the processing circuit 44 calculates the imaging time required to complete the imaging of the imaging range for each of the numbers of columns "n" and "n/2".

Here, the processing circuit 44 determines whether or not candidates for the number of columns have been specified based on the predetermined shooting time and the shooting time corresponding to the number of columns (step S506). If no candidate for the number of columns is identified (No at step S506), the processing circuit 44 adjusts the beam pitch (step S507), and proceeds to step S505 again.

On the other hand, if at least one candidate for the number of columns is specified (Yes at step S506), the processing circuitry 44 determines whether there are a plurality of candidates for the number of columns (step S508). Here, if there are a plurality of candidates for the number of columns (Yes at step S508), the processing circuit 44 receives an operation from the operator to select one of the candidates for the number of columns (step S509).

When there are not a plurality of candidates for the number of columns (No at step S508), such as when the number of columns that can complete imaging of the imaging range in a predetermined imaging time is only "n", or after step S509, the processing circuit 44 controls the permissible time for switching the tube voltage value supplied to the X-ray tube 11 by adjusting the number of columns of the detection element groups for which the DAS 18 collects signals (step S510).

Next, the processing circuit 44 causes the X-ray tube 11 to generate X-rays according to the imaging conditions set in step S503, and irradiates the subject P with the X-rays (step S511). At this time, the processing circuit 44 changes the X-ray energy for each one or a plurality of views by switching the tube voltage value supplied to the X-ray tube 11 . Further, the DAS 18 sequentially collects X-ray signals for each detection element group whose number of columns has been adjusted in step S510 to generate detection data. Further, the processing circuit 44 preprocesses the detection data output from the DAS 18 (step S512). The processing circuit 44 also generates CT image data based on the data (raw data) after preprocessing (step S513).

Here, processing circuit 44 determines whether or not to display a CT image (step S514). If a CT image is to be displayed, such as when a display instruction is received from the operator (Yes at step S514), the processing circuit 44 generates a CT image for display based on the CT image data, and displays the generated CT image. The image is displayed on the display 42 (step S515). On the other hand, if the CT image is not to be displayed (No at step S514), or after step S515, the processing circuit 44 determines whether or not to end the imaging (step S516). If the image capturing is not to be finished, such as when there is an additional image capturing (No at step S516), the processing circuit 44 proceeds to step S502 again. On the other hand, if it is determined to end the shooting (Yes at step S516), the processing circuit 44 ends the process.

It should be noted that if the photographing is not to be ended (No at step S516), the processing circuit 44 may proceed to step S501. That is, the processing circuitry 44 may acquire a predetermined imaging time for each imaging. Also, in this case, step S501 can be performed at any timing before step S506.

As described above, in the X-ray CT apparatus 1 according to the eighth embodiment, the DAS 18 collects signals based on the imaging range so that imaging is completed within a predetermined imaging time. to adjust. Specifically, the setting function 446 sets imaging conditions. Further, the adjustment function 445 specifies the number of selectable columns based on the shooting conditions set by the setting function 446, calculates the shooting time corresponding to the number of columns based on the specified number of columns and the shooting range, The number of columns for which the imaging time corresponding to the number of columns is shorter than the predetermined imaging time is specified as a candidate for the number of columns, and based on the candidate for the number of columns, the DAS 18 adjusts the number of columns of the detection element group for collecting signals. . Therefore, the X-ray CT apparatus 1 according to the eighth embodiment sets the imaging conditions first, thereby improving the flexibility of the imaging conditions and performing control so that the switching of the tube voltage value is completed within the allowable time. Furthermore, the photographing can be completed within a predetermined photographing time.

Further, as described above, the adjusting function 445 adjusts the shooting pitch when the number of rows (candidate for the number of rows) capable of completing shooting of the shooting range in a predetermined shooting time cannot be specified. That is, the adjustment function 445 adjusts the number of rows of the detection element group for signal collection by the DAS 18 and the pitch of imaging so that imaging is completed within a predetermined imaging time. Therefore, the X-ray CT apparatus 1 according to the eighth embodiment can perform predetermined imaging by adjusting the imaging pitch even when the imaging range is wide or when imaging conditions that tend to increase the imaging time are set. You can finish shooting in time.

(Ninth embodiment)
Although the fifth to eighth embodiments have been described so far, various different forms may be implemented other than the fifth to eighth embodiments described above.

In the fifth to eighth embodiments described above, cases where the processing circuit 44 of the X-ray CT apparatus 1 has the adjustment function 445 have been described. However, embodiments are not so limited. For example, an external device connected to the X-ray CT apparatus 1 via a network may have a function corresponding to the adjustment function 445.

For example, the X-ray CT apparatus 1 is connected to an imaging planning apparatus 5 via a network NW, as shown in FIG. The shooting planning device 5 is realized by computer equipment such as a workstation, for example. Note that FIG. 31 is a block diagram showing an example of the configuration of the imaging planning apparatus 5 according to the ninth embodiment.

Note that the location where the X-ray CT apparatus 1 and the imaging planning apparatus 5 are installed is arbitrary as long as they can be connected via the network NW. For example, the imaging planning device 5 may be installed in a hospital different from the X-ray CT device 1 . That is, the network NW may be configured by a closed local network within the hospital, or may be a network via the Internet. Although one X-ray CT apparatus 1 is shown in FIG. 31, the imaging planning apparatus 5 may be connected to a plurality of X-ray CT apparatuses 1 .

As shown in FIG. 31, the imaging planning device 5 has an input interface 51, a display 52, a memory 53, and a processing circuit .

The input interface 51 receives various input operations from the operator, converts the received input operations into electrical signals, and outputs the electrical signals to the processing circuit 54 . For example, the input interface 51 includes a mouse, a keyboard, a trackball, a switch, a button, a joystick, a touch pad that performs input operations by touching an operation surface, a touch screen that integrates a display screen and a touch pad, and an optical sensor. It is realized by the used non-contact input circuit, voice input circuit, or the like. Note that the input interface 51 may be composed of a tablet terminal or the like capable of wireless communication with the imaging planning apparatus 5 main body. Also, the input interface 51 is not limited to having physical operation parts such as a mouse and a keyboard. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the imaging planning apparatus 5 and outputs this electrical signal to the processing circuit 54 is also an example of the input interface 51. include.

The display 52 displays various information. For example, the display 52 displays a GUI for receiving various instructions, various settings, etc. from the operator via the input interface 51 . For example, display 52 is a liquid crystal display or a CRT display. The display 52 may be of a desktop type, or may be configured by a tablet terminal or the like capable of wireless communication with the main body of the imaging planning apparatus 5 .

The memory 53 is implemented by, for example, a RAM, a semiconductor memory device such as a flash memory, a hard disk, an optical disk, or the like. For example, the memory 53 stores programs for the circuits included in the imaging planning apparatus 5 to implement their functions. Note that the memory 53 may be realized by a server group (cloud) connected to the imaging planning apparatus 5 via the network NW.

The processing circuit 54 controls the overall operation of the imaging planning apparatus 5 by executing the adjustment function 541 and the notification function 542 . Here, the adjustment function 541 is an example of an adjustment unit. Also, the notification function 542 is an example of a notification unit.

In the imaging planning apparatus 5 shown in FIG. 31, each processing function is stored in the memory 53 in the form of a computer-executable program. The processing circuit 54 is a processor that implements a function corresponding to each program by reading the program from the memory 53 and executing the program. In other words, the processing circuit 54 in a state where each program has been read has a function corresponding to the read program.

Note that FIG. 31 shows a case where each processing function of the adjustment function 541 and the notification function 542 is implemented by a single processing circuit 54, but the embodiment is not limited to this. For example, the processing circuit 54 may be configured by combining a plurality of independent processors, and each processor may implement each processing function by executing each program. Moreover, each processing function of the processing circuit 54 may be appropriately distributed or integrated in a single or a plurality of processing circuits and implemented.

For example, the processing circuit 54 reads out a program corresponding to the adjustment function 541 from the memory 53 and executes it, thereby adjusting at least one of the number of columns and the number of channels of the detection element group from which the DAS 18 of the X-ray CT apparatus 1 acquires signals. is adjusted to control the allowable time for switching the tube voltage value supplied to the X-ray tube 11 . Further, the processing circuit 54 notifies the X-ray CT apparatus 1 of the adjustment result by the adjustment function 541 by reading out and executing a program corresponding to the notification function 542 from the memory 53 . 31, the X-ray CT apparatus 1 may not have the adjustment function 445. FIG.

For example, the adjustment function 541 controls at least one of the number of columns and the number of channels of the detection element group for signal acquisition by the DAS 18, thereby controlling the permissible time for switching the tube voltage value supplied to the X-ray tube 11. Then, the notification function 542 notifies the X-ray CT apparatus 1 of the adjustment result by the adjustment function 541 . For example, the notification function 542 notifies the X-ray CT apparatus 1 of the allowable time after control by the adjustment function 541 . In this case, the setting function 446 of the X-ray CT apparatus 1 sets the imaging conditions based on the notified allowable time. Alternatively, the adjustment function 541 may set the imaging conditions based on the post-control allowable time. In this case, the notification function 542 notifies the X-ray CT apparatus 1 of the imaging conditions set by the adjustment function 541 .

That is, the notification function 542 notifies the X-ray CT apparatus 1 of the allowable time after control by the adjustment function 541 or the imaging conditions as the adjustment result of the adjustment function 541 . Incidentally, when the adjustment function 541 sets the imaging conditions, the X-ray CT apparatus 1 may not have the setting function 446 .

To give another example, the adjusting function 541 acquires the imaging conditions set by the setting function 446 of the X-ray CT apparatus 1 via the network NW. Alternatively, the adjustment function 541 sets imaging conditions. Next, the adjustment function 541 adjusts at least one of the number of columns and the number of channels of the detection element group from which the DAS 18 collects signals based on the imaging conditions, thereby adjusting the tube voltage value supplied to the X-ray tube 11. controls the allowable time for switching. Next, the notification function 542 notifies the X-ray CT apparatus 1 of the result of adjustment by the adjustment function 541 . Here, if the setting function 446 has set the imaging conditions, the notification function 542 notifies the X-ray CT apparatus 1 of the allowable time after the control by the adjustment function 541 . Further, when the adjustment function 541 has set the imaging conditions, the notification function 542 notifies the X-ray CT apparatus 1 of the allowable time after control by the adjustment function 541 and the set imaging conditions.

That is, the notification function 542 notifies the X-ray CT apparatus 1 of the allowable time after the control by the adjusting function 541 or the allowable time after the control by the adjusting function 541 and the imaging condition as the result of adjustment by the adjusting function 541. do. Incidentally, when the adjustment function 541 sets the imaging conditions, the X-ray CT apparatus 1 may not have the setting function 446 .

Further, in the fifth to eighth embodiments described above, the case of performing dual energy acquisition has been described, but it is also possible to perform multi-energy acquisition using X-rays of three or more different energies. . For example, the system control function 441 sets the tube voltage value supplied to the X-ray tube 11 to a first tube voltage value V1, a second tube voltage value V2, and a third tube voltage value lower than the second tube voltage value V2. By switching between tube voltage values V3, the x-ray energy is varied for one or more views. Further, the adjusting function 445 or the adjusting function 541 adjusts at least one of the number of columns and the number of channels of the detection element group from which the DAS 18 collects signals so that the first tube voltage value V1 and the second tube voltage value The allowable time for switching the tube voltage value between V2 and the allowable time for switching the tube voltage value between the second tube voltage value V2 and the third tube voltage value V3 are controlled.

Further, in the fifth to eighth embodiments described above, a single-tube type X-ray CT apparatus has been described as an example of the X-ray CT apparatus 1 . However, the embodiment is not limited to this, and the X-ray CT apparatus 1 is a so-called multi-tube type X-ray CT apparatus in which a plurality of pairs of X-ray tubes and X-ray detectors are mounted on a rotating ring. It may be a device.

For example, the X-ray CT apparatus 1 has a pair of a first X-ray tube and a first X-ray detector and a pair of a second X-ray tube and a second X-ray detector. The X-ray CT apparatus 1 also includes a first DAS that sequentially collects X-ray signals for each detection element group in the first X-ray detector, and an X-ray detector for each detection element group in the second X-ray detector. and a second DAS for sequentially acquiring line signals.

In this case, the system control function 441, for example, switches the tube voltage value supplied to the first X-ray tube between the first tube voltage value V11 and the second tube voltage value V12, so that the X-ray is varied for one or more views. In addition, the adjustment function 445 or the adjustment function 541 adjusts at least one of the number of columns and the number of channels of the detection element group for which the first DAS collects signals, thereby adjusting the first tube voltage value V11 and the second tube voltage value V11. Controls the allowable time for switching the tube voltage value between the tube voltage value V12. Further, the system control function 441 switches the tube voltage value supplied to the second X-ray tube between the first tube voltage value V21 and the second tube voltage value V22, thereby reducing the X-ray energy. Change for one or more views. In addition, the adjustment function 445 or the adjustment function 541 adjusts at least one of the number of columns and the number of channels of the detection element group for which the second DAS collects signals, so that the first tube voltage value V21 and the second Controls the allowable time for switching the tube voltage value between the tube voltage value V22. This allows the system control function 441 to perform multi-energy acquisition by fast switching using X-rays of four different energies.

The term "processor" used in the above description includes, for example, a CPU, a GPU (Graphics Processing Unit), an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device ( Circuits such as Simple Programmable Logic Device (SPLD), Complex Programmable Logic Device (CPLD), and Field Programmable Gate Array (FPGA)). The processor implements its functions by reading and executing programs stored in the memory 41 or memory 53 .

1 and 12, it is assumed that the single memory 41 stores programs corresponding to each processing function. Also, in FIG. 31, the single memory 53 has been described as storing a program corresponding to each processing function. However, embodiments are not so limited. For example, a configuration may be adopted in which a plurality of memories 41 are distributed and the processing circuit 44 reads corresponding programs from the individual memories 41 . Further, for example, a configuration may be adopted in which a plurality of memories 53 are distributed and the processing circuit 54 reads corresponding programs from the individual memories 53 . Also, instead of storing the program in the memory 41 or memory 53, the program may be configured to be directly embedded in the circuit of the processor. In this case, the processor realizes its function by reading and executing the program embedded in the circuit.

Moreover, the processing circuit 44 and the processing circuit 54 may realize their functions using a processor of an external device connected via a network. For example, the processing circuit 44 reads and executes a program corresponding to each function from the memory 41, and uses an external workstation or cloud connected to the X-ray CT apparatus 1 via the network NW as computational resources. , each function shown in FIGS. 1 and 12 is realized. Further, for example, the processing circuit 54 reads and executes a program corresponding to each function from the memory 53, and uses an external workstation or cloud connected to the imaging planning apparatus 5 via the network NW as computational resources. Thereby, each function shown in FIG. 31 is realized.

Each component of each device according to the above-described embodiments is functionally conceptual, and does not necessarily need to be physically configured as illustrated. That is, the specific form of distribution/integration of each device is not limited to the illustrated one, and all or part of them can be functionally or physically distributed/integrated in arbitrary units according to various loads and usage conditions. Can be integrated and configured. Furthermore, all or any part of each processing function performed by each device can be implemented by a CPU and a program analyzed and executed by the CPU, or implemented as hardware based on wired logic.

Moreover, the control method described in the above embodiments can be realized by executing a control program prepared in advance on a computer such as a personal computer or a work station. This control program can be distributed via a network such as the Internet. In addition, this control program is recorded on a computer-readable recording medium such as a hard disk, flexible disk (FD), CD-ROM, MO, DVD, etc., and can be executed by being read from the recording medium by a computer.

According to at least one embodiment described above, a sequential acquisition DAS can be used to enable fast switching dual energy acquisition or multi-energy acquisition.

While several embodiments of the invention have been described, these embodiments have been presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and modifications can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, as well as the scope of the invention described in the claims and equivalents thereof.

1 X-ray CT apparatus 11 X-ray tube 12 X-ray detector 18 DAS
44 processing circuit 441 system control function 442 preprocessing function 443 generation function 444 output function 445 adjustment function 446 setting function

Claims (20)

an X-ray generator that generates X-rays;
an X-ray detection unit having first to n-th (n is an integer equal to or greater than 2) detection element groups for detecting X-rays transmitted through a subject and accumulating charges generated by the detection;
a collection unit that collects detection data for each view by repeating a process of reading charges accumulated in the first to n-th detection element groups in order from the first detection element group in group units;
While periodically varying the energy of the X-rays irradiating the subject and collecting detection data for one or a plurality of consecutive views, the average energy of the X-rays irradiating the subject is: a control unit that controls the X-ray generation unit so that the detection element groups are substantially equal;
with
After the collection unit finishes reading the charge in a first view, the control unit controls the time period until the collection unit starts reading the charge in a second view after the first view. (2) an X-ray CT apparatus that changes the energy of the X-rays ; In a plurality of views from the second view to a third view subsequent to the second view, the control unit controls the X-ray at least while the collection unit is reading out the charges. 2. An X-ray CT apparatus according to claim 1 , wherein the energy is kept constant. an X-ray generator that generates X-rays;
an X-ray detection unit having first to n-th (n is an integer equal to or greater than 2) detection element groups for detecting X-rays transmitted through a subject and accumulating charges generated by the detection;
a collection unit that collects detection data for each view by repeating a process of reading charges accumulated in the first to n-th detection element groups in order from the first detection element group in group units;
While periodically varying the energy of the X-rays irradiating the subject and collecting detection data for one or a plurality of consecutive views, the average energy of the X-rays irradiating the subject is: a control unit that controls the X-ray generation unit so that the detection element groups are substantially equal;
with
After the collection unit finishes reading the charge in a first view, the control unit controls the time period until the collection unit starts reading the charge in a second view after the first view. 2, wherein the energy of the X-ray is changed from the first energy to the second energy and then changed from the second energy to the first energy. 4. The X-ray CT apparatus according to any one of claims 1 to 3 , wherein said controller changes the energy of said X-rays by controlling the tube voltage supplied to said X-ray generator. The X-ray generator generates X-rays with energy corresponding to the applied tube voltage,
The collecting unit collects charges accumulated in the first to m-th (m is an integer equal to or more than n and equal to or less than n) detection element groups among the first to n-th detection element groups to the first detection element group. Detected data for each view is collected by repeating the process of reading in units of groups in order from the detection element group,
The control unit periodically switches the tube voltage, and after the collection unit finishes reading the charges in the first view, the collection unit starts reading the charges in the second view. 2. The X-ray CT apparatus according to claim 1, wherein switching of said tube voltage is performed within a permissible time, which is a period of time until said switching and is a period of length corresponding to said m . 6. An adjustment unit for controlling the permissible time by adjusting at least one of the number of columns and the number of channels of the detection element group from which the collection unit reads out the charges, thereby adjusting the m. The X-ray CT apparatus according to . 7. The X-ray CT according to claim 6 , further comprising a setting unit that sets imaging conditions including at least one of a tube voltage value and a tube voltage value so that the tube voltage can be switched within the allowable time. Device. 8. The X-ray CT apparatus according to claim 7 , wherein said setting unit sets said imaging conditions by changing preset conditions set in advance. 8. The X-ray CT apparatus according to claim 7 , wherein said setting unit newly sets said imaging conditions. further comprising a setting unit for setting shooting conditions,
The adjustment unit controls the allowable time by adjusting at least one of the number of columns and the number of channels based on the imaging conditions set by the setting unit to adjust the m . 7. The X-ray CT apparatus according to 6 . The X-ray CT apparatus according to any one of claims 7 to 10 , wherein said setting unit sets a tube current value of said X-ray generation unit as said imaging condition. 12. The X according to claim 11 , wherein the setting unit sets a lower limit of selectable tube current values based on the allowable time, and sets the tube current value of the X-ray generating unit so as to exceed the lower limit. Line CT device. The X-ray CT apparatus according to any one of claims 7 to 12 , wherein said setting unit sets said tube voltage supplied to said X-ray generation unit as said imaging condition. The setting unit sets a first tube voltage and a second tube voltage as the tube voltages to be supplied to the X-ray generation unit,
The control unit switches the tube voltage supplied to the X-ray generation unit between the first tube voltage and the second tube voltage, thereby changing the energy of the X-rays to one or more views. 14. The X-ray CT apparatus according to claim 13 , which is changed every time. 7. The X-ray CT apparatus according to claim 6 , wherein said adjustment unit adjusts at least one of said number of columns and said number of channels based on an imaging range so that imaging is completed within a predetermined imaging time. The adjustment unit calculates an imaging time corresponding to the number of columns based on the imaging range, specifies the number of columns in which the calculated imaging time is shorter than the predetermined imaging time as a candidate for the number of columns, and 16. The X-ray CT apparatus according to claim 15 , wherein the collection unit adjusts the number of columns of the detection element group from which the charges are read out. further comprising a setting unit for setting shooting conditions,
The adjustment unit identifies the number of selectable columns based on the imaging conditions set by the setting unit, calculates the imaging time corresponding to the number of columns based on the identified number of columns and the imaging range, The number of columns for which the calculated imaging time is shorter than the predetermined imaging time is specified as a candidate for the number of columns, and the collection unit adjusts the number of columns of the detection element group from which the charges are read based on the candidates. 16. The X-ray CT apparatus according to claim 15 . 18. The adjusting unit according to any one of claims 15 to 17 , wherein the adjustment unit adjusts at least one of the number of columns and the number of channels and a shooting pitch so that shooting is completed within the predetermined shooting time. 's X-ray CT apparatus. The X-ray CT apparatus according to any one of claims 15 to 18 , wherein said predetermined imaging time is a breath-holding time. 20. The adjusting unit adjusts at least one of the number of columns and the number of channels by adjusting bundling conditions when the collecting unit reads out the charges. X-ray CT apparatus as described.

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