JP6958849B2 - X-ray computed tomography equipment - Google Patents

Description

An embodiment of the present invention relates to an X-ray computed tomography apparatus.

Clinically, there is a need to observe the displacement of the knee joint in periodic dynamics such as gait dynamics. On the other hand, although it is not gait dynamics, as a reconstruction method applied to periodic dynamics, electrocardiographic synchronous reconstruction and reconstruction are performed by extracting and synthesizing arbitrary data from continuous scan data based on a synchronous signal. Respiratory synchronous reconstruction is known. This type of reconstruction can be broadly divided into half reconstruction and segment reconstruction.

JP-A-2009-28065

The above reconstruction method has no particular problem when applied to the heart or lungs.
However, according to the study of the present inventor, when half-reconstruction and segment-reconstruction are applied to gait dynamics, reconstruction in the heart and lungs is performed in that the target moves a large distance and there is no resting phase. It is different from the configuration.

Therefore, when the reconstruction is applied to gait dynamics, it is necessary to achieve a time resolution higher than the time resolution normally achievable by the reconstruction in the heart or lungs. In the case of half reconstruction, the time resolution that can be achieved in principle is up to half of the collection speed, so it is difficult to apply it to gait dynamics. In the case of segment reconstruction, the time resolution can be improved by increasing the number of collected data in theory, but the range that can be collected is limited by the relationship between the cycle of the synchronization signal and the rotation speed of the X-ray tube. is expected. For example, when the walking cycle and the rotation speed of the X-ray tube match, the direction in which data can be collected is restricted to one direction.

An object is to provide an X-ray computed tomography apparatus capable of capturing periodic dynamics even in the absence of a stationary phase.

The X-ray computed tomography apparatus according to the embodiment includes a gantry, a setting means, an acquisition means, and a notification means.

The gantry can scan the subject.

The setting means sets the imaging conditions of the subject.

The acquisition means acquires the optimum dynamic cycle of the subject based on the imaging conditions.

The notification means notifies the subject of the dynamic cycle.

FIG. 1 is a schematic diagram showing an outline when the segment reconstruction common to each embodiment is applied to gait dynamics. FIG. 2 is a schematic diagram showing a schematic configuration of an X-ray computed tomography apparatus according to the first embodiment. FIG. 3 is a schematic view showing the configuration of the X-ray computed tomography apparatus according to the same embodiment. FIG. 4 is a schematic view showing a modified configuration of the measurement / notification device in the same embodiment. FIG. 5 is a schematic view showing an example of a modified configuration of the measurement / notification device in the same embodiment. FIG. 6 is a flowchart for explaining the operation in the same embodiment. FIG. 7 is a schematic diagram for explaining the operation in the same embodiment. FIG. 8 is a schematic diagram for explaining the operation in the same embodiment for each timing. FIG. 9 is a schematic diagram for explaining the operation in the same embodiment for each timing. FIG. 10 is a schematic diagram for explaining the operation in the same embodiment for each timing. FIG. 11 is a schematic diagram for explaining the operation in the same embodiment. FIG. 12 is a schematic diagram for explaining a modified example of the operation in the same embodiment. FIG. 13 is a flowchart for explaining a first modification in the same embodiment. FIG. 14 is a flowchart for explaining a second modification of the embodiment. FIG. 15 is a schematic diagram showing a schematic configuration of an X-ray computed tomography apparatus according to a second embodiment. FIG. 16 is a schematic diagram showing an example of a schematic configuration of an X-ray computed tomography apparatus according to a third embodiment. FIG. 17 is a schematic view showing another example of the schematic configuration in the same embodiment. FIG. 18 is a flowchart for explaining the operation in the same embodiment. FIG. 19 is a schematic diagram for explaining the X-ray computed tomography apparatus according to the fourth embodiment.

Hereinafter, the X-ray computed tomography apparatus according to each embodiment will be described with reference to the drawings, but before that, FIG. 1 is used for an outline when the segment reconstruction common to each embodiment is applied to gait dynamics. Will be described.

In segment reconstruction, the time resolution can be improved by adjusting the relationship between the cycle of the synchronization signal and the rotation speed of the gantry. Generally, in the electrocardiographic synchronous reconstruction, the rotation speed is adjusted because the heartbeat is difficult to control.

On the other hand, in each embodiment, since it is easy to control walking, the walking cycle is adjusted by the person himself / herself. In FIG. 1, the subject P is walking while adjusting (maintaining) the walking cycle to W seconds. At this time, in the segment reconstruction, X-rays are exposed from the X-ray tube that orbits around the subject P only in a specific phase range in which the subject P takes substantially the same posture (intermittent exposure). The substantially same postures are, for example, the shaded postures in the upper part of FIG. 1 and the postures corresponding to the footprints in the circle in the middle part of FIG. Here, for example, it is assumed that the rotation speed of the X-ray tube (time per rotation of the X-ray tube) is R [seconds / rotation], and the exposure time in a specific phase range is S [seconds]. The cycle in which the subject P during walking takes substantially the same posture is the walking cycle W. Therefore, in the segment reconstruction, exposure of S [seconds] is performed every walking cycle W from time t = 0. The range of projection data of each segment obtained by such exposure is S / R (eg, 1/8) of the range of projection data obtained by exposure for one rotation. Therefore, in the segment reconstruction, the projection data of R / S segments (eg, 8) is collected in the walking cycle of R / S times (eg, 8 times), and the data for one rotation is synthesized. ..

The above is an outline when the segment reconstruction common to each embodiment is applied to gait dynamics. The segment reconstruction of each embodiment is not limited to walking dynamics, as long as it is a dynamic in which the repetition cycle can be adjusted by the person himself / herself, such as running dynamics, dynamics in which elbow bending and stretching are repeated, or respiratory dynamics. , Applicable. Further, the X-ray computed tomography apparatus is not limited to a standing CT apparatus suitable for gait dynamics, and may be a normal CT apparatus (decubitus CT apparatus) suitable for dynamics in which elbows are repeatedly bent and stretched. .. Subsequently, the first embodiment will be specifically described.

<First Embodiment>
2 and 3 are schematic views showing the configuration of the X-ray computed tomography apparatus according to the first embodiment. The X-ray computed tomography apparatus according to the present embodiment includes a gantry device 10, an image reconstruction device 51, and an operation console (console) 52. For example, the gantry device 10 is installed in the CT examination room, and the image reconstruction device 51 and the operation console 52 are installed in the control room adjacent to the CT examination room. The gantry device 10, the image reconstruction device 51, and the console 52 are connected by wire or wirelessly so as to be able to communicate with each other. The gantry device 10 is a scanning device having a configuration for performing X-ray computed tomography (hereinafter, referred to as X-ray CT imaging) of a subject P in a standing or lying position. In the present embodiment, the gantry device 10 has an X-ray tube 17 that rotates around the subject P and intermittently exposes the subject P to X-rays, and an X-ray detection that detects the X-rays that have passed through the subject P. It is a device having a vessel 19 and capable of scanning a subject P. The gantry device 10 is used as a device for collecting raw data of a plurality of segments by the scan. The collected projection data is used for segment reconstruction by the image reconstruction device 51. The console 52 is a computer that controls the gantry device 10.

As shown in FIG. 3, the gantry main body 11 is a substantially cylindrical structure in which an opening 15 forming a field of view is formed. The gantry main body 11 accommodates an X-ray tube 17 and an X-ray detector 19 arranged so as to face each other with the opening 15 interposed therebetween.

More specifically, the gantry main body 11 includes a main frame (not shown) formed of a metal such as aluminum, and a rotating frame 21 rotatably supported by the main frame around the central axis R1 via bearings or the like. Further has. An annular electrode (not shown) is provided at a contact portion of the main frame with the rotating frame 21. A conductive slider (not shown) is attached to the contact portion of the main frame so as to make sliding contact with the annular electrode. The rotating frame 21 is a metal frame formed in a ring shape by a metal such as aluminum, and for example, an X-ray tube 17 and an X-ray detector 19 are attached. The X-ray tube 17 and the X-ray detector 19 may be fitted into a recess formed in the rotating frame 21, or may be fastened with a fastener such as a screw.

The rotating frame 21 receives power from the rotation driving device 23 and rotates around the central axis R1 at a constant angular velocity. The rotation speed of the rotation frame 21 is the rotation speed of the X-ray tube 17, and is also referred to as the gantry rotation speed. Since the "rotation speed" is the time per rotation, it may be called the "rotation period". The rotation drive device 23 generates power for rotating the rotation frame 21 according to the control from the gantry control circuit 25. The rotation drive device 23 generates power by driving at a rotation speed corresponding to the duty ratio and the like of the drive signal from the gantry control circuit 25. The rotation drive device 23 is realized by, for example, a motor such as a direct drive motor or a servo motor. The rotation drive device 23 is housed in, for example, the gantry main body 11.

The support column 13 is a base that supports the gantry body 11 away from the floor surface. The support column 13 has a columnar shape such as a columnar shape or a prismatic shape. The strut 13 is formed of any substance such as plastic or metal. The support column 13 is attached to, for example, a side surface portion of the gantry main body 11. In order to take an X-ray CT image of the subject P in a standing position, the support column 13 slidably supports the gantry main body 11 in a state where the central axis R1 of the opening 15 is maintained in the direction perpendicular to the ground plane.

Typically, the columns 13 are provided on both sides of the gantry body 11. However, this embodiment is not limited to this. For example, one support column 13 may be connected to only one side of both side portions of the gantry main body 11. Further, although the support column 13 has a columnar shape, the present embodiment is not limited to this. For example, the support column 13 may have any shape such as a U shape as long as it can support at least one side portion of the gantry body.

The support column 13 does not need to fix the gantry body 11 so that the central axis R1 faces perpendicular to the floor surface. That is, the support column 13 may be configured to rotatably support the gantry main body 11 around a horizontal axis (hereinafter, referred to as a tilt axis) parallel to the floor surface. In this case, the support column 13 and the gantry main body 11 may be connected to each other via bearings or the like so that the gantry main body 11 can rotate around the tilt axis. As a result, it is possible to selectively execute the standing position photographing and the lying position photographing by one gantry device 10.

As shown in FIG. 3, the support column 13 accommodates a drive device (hereinafter, referred to as a support device drive device) 27 for sliding the gantry main body 11 in the vertical direction. The strut drive device 27 generates power for sliding the gantry main body 11 in the vertical direction according to the control from the gantry control circuit 25. Specifically, the support column drive device 27 generates power by driving at a rotation speed corresponding to the duty ratio of the drive signal from the gantry control circuit 25 and the like. The support column 13 receives power from the support column drive device 27 and slides the gantry main body 11 in the vertical direction with respect to the support column 13. The strut drive device 27 is realized by a motor such as a servo motor, for example.

As shown in FIGS. 2 and 3, a measurement / notification device 29 is provided below the gantry main body 11. The measurement / notification device 29 is a device that integrates the measurement device and the notification device, and can transmit and receive various information to and from the system control circuit 61 of the console 52 via the gantry control device 25 and the device control device 39. It has become. As the measurement / notification device 29, for example, a walking control device such as a treadmill is used. The treadmill has a first roller driven by a driving device (not shown), a rotatable second roller, and a belt that transmits the rotation of the first roller to the second roller, and the belt transmits the subject P. Support walking. Such a treadmill has a notification function of notifying the subject P of the walking cycle by operating at an operating speed (moving speed of the belt) according to the walking cycle to be notified to the subject P. In addition to this, the treadmill has a measuring function of measuring the walking cycle of the subject P by operating at an operating speed (moving speed of the belt) corresponding to the walking speed preferred by the subject P. Supplementally, the operating speed of the treadmill and the walking cycle of the subject P are related to each other as one becomes larger and the other becomes smaller. Therefore, the measurement function can derive the walking cycle of the subject P based on the empirical formula or table expressing this relationship and the operating speed of the treadmill. Alternatively, the measurement function is based on the preset stride length (L [m / 2 stride length]) of the subject P for two steps and the operating speed of the treadmill (V [m / sec]). The walking cycle W (= L / V [seconds / 2 steps]) of the sample P may be calculated. The above [m / 2 stride] and [second / 2 stride] may be read as [m / cycle] and [second / cycle], respectively. That is, walking for two steps corresponds to one cycle of gait dynamics. A drive device (not shown) generates power by driving at a rotation speed corresponding to a duty ratio or the like of a drive signal from the device control circuit 39. The drive device is realized by, for example, a motor such as a direct drive motor or a servo motor.

The device control circuit 39 controls the measurement / notification device 29 according to the control from the gantry control circuit 25. As hardware resources, the device control circuit 39 includes a processing device (processor) such as a CPU (Central Processing Unit) and an MPU (Micro Processing Unit) and a storage device (a storage device) such as a ROM (Read Only Memory) and a RAM (Random Access Memory). It has a memory). The device control circuit 39 includes an application specific integrated circuit (ASIC), a field programmable logic device (FPGA), and another complex programmable logic device (FPGA). It may be realized by CPLD) or Simple Programmable Logic Device (SPLD). The processing device realizes the above function by reading and executing the program stored in the storage device. Instead of storing the program in the storage device, the program may be directly incorporated in the circuit of the processing device. In this case, the processing device realizes the above function by reading and executing the program incorporated in the circuit.

An operating condition storage circuit 41 is connected to the device control circuit 39. The operating condition storage circuit 41 is a storage device that stores a plurality of operating conditions related to the periodic motion of the subject P. Specifically, the operating condition storage circuit 41 stores a LUT (Look Up Table) that stores a plurality of operating conditions. Hereinafter, a LUT that stores a plurality of operating conditions will be referred to as an operating condition table.

The operating condition is information for operating the notification device according to the imaging condition. For example, the optimum walking cycle W_opt of the subject P is notified according to the rotation speed R (imaging condition) of the X-ray tube 17. Contains information for. As the information for notifying the optimum walking cycle W_opt, appropriate information is set in advance according to the notification device. For example, when the notification device is a treadmill, the information for notifying the walking cycle W_opt is the operating speed of the treadmill corresponding to the walking cycle W_opt. When the notification device is a display, the information for notifying the optimum walking cycle W_opt is, for example, a moving image file for displaying a moving image corresponding to the walking cycle W_opt. When the notification device is a speaker, the information for notifying the optimum walking cycle W_opt is, for example, an audio file for outputting the voice corresponding to the walking cycle W_opt. The device control circuit 39 controls the drive device of the measurement / notification device 29 according to the operating conditions based on the photographing conditions specified by the user among the plurality of operating conditions stored in the operating condition storage circuit 41.

The measurement / notification device 29 is not limited to the device having the measurement function and the notification function, and may be provided as separate measurement device 29a and notification device 29b as shown in FIG. As the measuring device 29a, for example, as shown in FIG. 5, the dynamic cycle of the subject P may be measured by using the optical camera 29a1 or the pressure sensor 29a2. For example, the optical camera 29a1 can support the calculation of the walking cycle of the subject P as the time corresponding to the moving image of two steps of the subject P by photographing the walking dynamics of the subject P together with the time information. It has become. For the walking cycle for two steps, the average value may be calculated, for example, by dividing the walking cycle for the number of steps that is an integral multiple of two steps by the integer. Further, as the measuring device 29a using a camera, for example, Kinect (registered trademark) can be used. Alternatively, an acceleration sensor may be attached to the foot of the subject as a measuring device 29a that does not use a camera. The pressure sensor 29a2 is, for example, a device capable of detecting the pressure from the right foot or the left foot of the subject P. Since the fluctuation cycle of the output signal of the pressure sensor 29a2 is the cycle of the pressure received from one leg of the subject P, it corresponds to the walking cycle of the subject P. The pressure sensor 29a2 shows a configuration in which the pressures of the right foot and the left foot of the subject P are individually detected in FIG. 5, but the pressure sensor 29a2 is not limited to this and may detect the pressure of the right foot or the left foot of the subject P. Just do it. As the notification device 29b, a device that stimulates the sight or hearing of the subject P, such as a laser, an LED, a display device, a speaker, or a metronome, can be appropriately used. Further, the notification device 29b is not limited to a device that stimulates vision and hearing, and a treadmill that does not have a walking cycle measurement function may be used.

As shown in FIG. 1, the X-ray tube 17 generates X-rays by receiving a high voltage applied from the high voltage generator 43. The high voltage generator 43 is attached to, for example, the rotating frame 21. The high voltage generator 43 generates a high voltage to be applied to the X-ray tube 17 under the control of the gantry control circuit 25 from the electric power supplied from the power supply device (not shown) of the gantry main body 11 via the annular electrode. The high voltage generator 43 and the X-ray tube 17 are connected via a high voltage cable (not shown). The high voltage generated by the high voltage generator 43 is applied to the X-ray tube 17 via the high voltage cable.

The X-ray detector 19 detects X-rays generated from the X-ray tube 17 and transmitted through the subject P. The X-ray detector 19 is equipped with a plurality of X-ray detection elements (not shown) arranged on a two-dimensional curved surface. Each X-ray detection element detects X-rays from the X-ray tube 17 and converts them into an electric signal having a peak value corresponding to the intensity of the detected X-rays. Each X-ray detector has, for example, a scintillator and a photoelectric converter. The scintillator receives X-rays and emits fluorescence. The photoelectric converter converts the generated fluorescence into charge pulses. The charge pulse has a peak value according to the intensity of X-rays. Specifically, as the photoelectric converter, a device such as a photomultiplier tube or a photodiode that converts a photon into an electric signal is used. The X-ray detector 19 according to the present embodiment is not limited to an indirect detection type detector that temporarily converts X-rays into fluorescence and then converts them into an electric signal, and directly converts X-rays into an electric signal. It may be a direct detection type detector.

The data collection circuit 45 collects digital data indicating the intensity of X-rays attenuated by the subject P for each view. The data collection circuit 45 is realized, for example, by a semiconductor integrated circuit in which an integrator circuit provided for each of a plurality of X-ray detection elements and an A / D converter are mounted in parallel. The data collection circuit 45 is connected to the X-ray detector 19 in the gantry main body 11. The integrator circuit integrates the electrical signal from the X-ray detector over a predetermined view period to generate an integrator signal. The A / D converter A / D-converts the generated integrated signal to generate digital data having a data value corresponding to the peak value of the integrated signal. The converted digital data is called raw data. Raw data is a set of digital values of X-ray intensity identified by the channel number, column number, and view number indicating the collected view of the source X-ray detector. The raw data is supplied to the image reconstructing device 51 via, for example, a non-contact data transmission device (not shown) housed in the gantry main body 11.

The gantry main body 11 is required not only for the above-mentioned X-ray tube 17, X-ray detector 19, rotating frame 21, main frame, power supply device, high voltage generator 43, and data collection circuit 45, but also for CT imaging. Other various devices may be accommodated. For example, a cooling device for cooling the X-ray tube may be attached to the rotating frame 21. Further, a fan for air conditioning may be attached to the gantry main body 11.

The gantry control circuit 25 controls the high voltage generator 43, the rotation drive device 23, the support column drive device 27, and the device control circuit 39 according to the control from the system control circuit 61 of the console 52. The gantry control circuit 25 has a processing device (processor) such as a CPU and MPU and a storage device (memory) such as a ROM and RAM as hardware resources. Further, the gantry control circuit 25 may be realized by an ASIC, FPGA, CPLD, SPLD or the like. The processing device realizes the above function by reading and realizing a program stored in the storage device. Instead of storing the program in the storage device, the program may be directly incorporated in the circuit of the processing device. In this case, the processing device realizes the above function by reading and executing a program incorporated in the circuit.

The device control circuit 39 and the gantry control circuit 25 may be realized by a single circuit. Further, the device control circuit 39, the operating condition storage circuit 41, and the gantry control circuit 25 may be mounted on a plurality of boards or may be mounted on a single board. The device control circuit 39, the operating condition storage circuit 41, and the gantry control circuit 25 may be provided on the support column 13 of the gantry main body 11 or on the console 52. The device control circuit 39 and the gantry control circuit 25 do not have to be provided in the same device, and may be provided in separate devices.

As shown in FIG. 3, the console 52 includes an image processing device 53, a display device 55, an input device 57, a main memory circuit 59, and a system control circuit 61. Data communication between the image processing device 53, the display device 55, the input device 57, the main memory circuit 59, and the system control circuit 61 is performed via a bus. The console 52 is connected to the image reconstruction device 51 via a data line.

The image reconstruction device 51 generates a CT image (reconstruction image) by segment reconstruction processing using the raw data of the plurality of segments collected by scanning the subject P by the gantry device 10. Specifically, the image reconstruction device 51 includes a preprocessing unit 511, a projection data storage unit 513, and a reconstruction calculation unit 515. The pre-processing unit 511 preprocesses the raw data from the gantry device 10. The pre-processing includes various correction processing such as logarithmic conversion, X-ray intensity correction, and offset correction. The raw data after preprocessing is called projection data. The projection data storage unit 513 is a storage device such as an HDD, SSD, or integrated circuit storage device that stores the projection data generated by the preprocessing unit 511. The reconstruction calculation unit 515 generates a CT image expressing the spatial distribution of CT values with respect to the subject P by segment reconstruction processing based on the projection data. Image reconstruction algorithms include analytical image reconstruction methods such as the FBP (filtered back projection) method and CBP (convolution back projection) method, the ML-EM (maximum likelihood expectation maximization) method, and the OS-EM (ordered subset). An existing image reconstruction algorithm such as a statistical image reconstruction method such as the expectation maximization method may be used.

The image reconstruction device 51 has a processing device (processor) such as a CPU, MPU, and GPU (Graphics Processing Unit) and a storage device (memory) such as a ROM and RAM as hardware resources. Further, the image reconstruction device 51 may be realized by an ASIC, an FPGA, a CPLD, or a SPLD. The processing device realizes the functions of the preprocessing unit 511 and the reconstruction calculation unit 515 by reading and executing the program stored in the storage device. Instead of storing the program in the storage device, the program may be directly incorporated in the circuit of the processing device. In this case, the processing device realizes the functions of the preprocessing unit 511 and the reconstruction calculation unit 515 by reading and executing the program incorporated in the circuit. Further, a dedicated hardware circuit that functions as the preprocessing unit 511 and a dedicated hardware circuit that functions as the reconstruction calculation unit 515 may be mounted on the image reconstruction device.

The image processing device 53 performs various image processing on the CT image reconstructed by the image reconstructing device 51. For example, when the CT image is volume data, the image processing apparatus 53 performs volume rendering, surface volume rendering, image value projection processing, MPR (Multi-Planer Reconstruction) processing, CPR (Curved MPR) processing, and the like on the CT image. A display image is generated by performing three-dimensional image processing. The image processing device 53 has a processing device (processor) such as a CPU, MPU, and GPU and a storage device (memory) such as a ROM and RAM as hardware resources. Further, the image processing device 53 may be realized by an ASIC, an FPGA, a CPLD, or a SPLD.

The display device 55 displays various information such as a two-dimensional CT image and a display image. As the display device 55, for example, a CRT display, a liquid crystal display, an organic EL display, an LED display, a plasma display, or any other display known in the art can be appropriately used.

The input device 57 receives various commands and information inputs from the user. As the input device 57, a keyboard, a mouse, various switches, and the like can be used. The input device 57 may be provided on the operation console 52 or on the gantry device 10.

The main storage circuit 59 is a storage device such as an HDD, an SSD, or an integrated circuit storage device that stores various information. Further, the main storage circuit 59 may be a drive device or the like that reads and writes various information to and from a portable storage medium such as a CD-ROM drive, a DVD drive, or a flash memory. For example, the main storage circuit 59 stores a control program or the like related to CT imaging according to the present embodiment.

The system control circuit 61 has the above-mentioned processing device and storage device as hardware resources. The system control circuit 61 functions as the center of the X-ray computed tomography apparatus according to the present embodiment. Specifically, the system control circuit 61 reads out the control program stored in the main storage circuit 59, expands it on the memory, and controls each part of the X-ray computed tomography apparatus according to the expanded control program.

The image reconstruction device 51, the image processing device 53, and the system control circuit 61 may be integrated on a single board in the console 52, or may be distributed and mounted on a plurality of boards.

Next, the operation of the X-ray computed tomography apparatus configured as described above will be described with reference to the flowchart of FIG. 6 and the schematic views of FIGS. 7 to 12.

In the stage prior to the X-ray CT imaging, the subject P is guided by an operator such as a medical worker to a treadmill which is a measurement / notification device 29 and stands on the treadmill. Subsequently, the subject P walks on the treadmill when the treadmill is operated by the operation of the operator. The operating speed of the treadmill is adjusted to the normal walking speed of the subject P by the operation of the operator. Hereinafter, the normal walking speed is referred to as a basic walking speed.

While the subject P is walking at the basic walking speed, the measurement / notification device 29 and the console 52 measure the dynamic cycle of the subject P (step ST10). In this example, the measured dynamic cycle is the basic gait cycle. The system control circuit 61 of the console 52 calculates the basic walking cycle W_measure [seconds / cycle] of the subject P based on the operating speed V [m / sec] of the treadmill received from the measurement / notification device 29. Alternatively, as shown in FIG. 5, the system control circuit 61 may derive the basic walking cycle W_measure of the subject P by using the optical camera 29a1 or the pressure sensor 29a2. In any case, the system control circuit 61 stores the measured basic walking cycle W_measure in the main memory circuit 59.

Subsequently, the system control circuit 61 sets the imaging conditions based on the obtained dynamic period (step ST20). For example, on the console 52, the imaging conditions (scan conditions) suitable for the purpose of the inspection are input by the operation of the input device 57 by the operator. The shooting conditions are X-ray conditions (tube voltage, tube current, X-ray exposure time), gantry rotation speed R [seconds / rotation] (rotation speed of rotation frame 21 [seconds / rotation]), and collected data for each cycle. Includes existing parameters for X-ray CT imaging, such as range length S [seconds] (1 / integer of R). The length S [seconds] of the collected data range for each cycle corresponds to the exposure time [seconds] for each cycle. Here, the input shooting conditions are set in the main storage circuit 59 and transmitted to the gantry control circuit 25 by the system control circuit 61.

Next, the system control circuit 61 acquires the optimum dynamic period based on the set imaging conditions (step ST30). For example, the system control circuit 61 compares the stored basic walking cycle W_measure [seconds / cycle] with the set gantry rotation speed R, and derives the parameter A by the equation (2) described later. After that, the system control circuit 61 acquires the optimum walking cycle W_opt of the subject P based on, for example, the following equation (1).

W_opt = A × R ± S ・ ・ ・ (1)
Here, the parameter S is a value in which an integral multiple of S is R (however, 2S <R, to exclude half reconstruction). Further, the term of A × R in the equation (1) is a value of an even multiple (excluding 0) of S. In this case, the term "± S" in the equation (1) may be transformed into a term for adding or subtracting an odd multiple of S, such as "± 3S", "± 5S", or "± 7S". good. That is, the walking cycle W_opt is optimal if it has a value different from R and an odd multiple of S. This is because when W_opt and R have the same value, the direction in which data can be collected is restricted in one direction. Further, when W_opt is an even multiple of S, the direction in which data can be collected is restricted to half of all segments (direction of every other segment). When the odd multiple of S is A × R, the term “± S” in the equation (1) is an even multiple of S, such as “± 2S”, “± 4S”, or “± 6S”. However, it may be transformed into a term for adding or subtracting (excluding 0 times).

The parameter A is, for example, an integer value satisfying the equation (2).

Int (W_measure / R) <A ≤ Int (W_measure / R) +1 ... (2)
A table in which a combination of parameters satisfying the above conditions is set in advance may be held in the main storage circuit 59, and the parameters may be read from the table, or the parameters may be calculated for each inspection. In any case, it suffices if the system control circuit 61 can acquire the optimum dynamic period.

After step ST30, the console 52 and the measurement / notification device 29 notify the subject P of the acquired optimum dynamic cycle (step ST40). For example, the system control circuit 61 sends the optimum walking cycle W_opt to the gantry control circuit 25. The gantry control circuit 25 supplies the optimum walking cycle W_opt to the device control circuit 39. The device control circuit 39 reads information indicating the operating speed of the treadmill corresponding to the optimum walking cycle W_opt from the operating condition storage circuit 41. Then, the device control circuit 39 drives the treadmill according to the read information. The subject P walks on the treadmill when the treadmill is operated by the operation of the operator. The operating speed of the treadmill is adjusted to the walking speed corresponding to the optimum walking cycle W_opt. As a result, the optimum walking cycle W_opt is notified to the subject P walking on the treadmill. The notification of the optimum walking cycle W_opt by step ST40 is continuously executed until the end of CT imaging.

While the subject P is walking in the optimum walking cycle W_opt, the console 52 transmits a scan start instruction to the gantry control circuit 25 by the operation of the operator.

The gantry control circuit 25 controls the rotation drive device 23, the support column drive device 27, the device control circuit 39, and the high voltage generator 43 in accordance with the scan start instruction, and mounts the subject P walking on the treadmill. X-ray CT imaging is performed by the main body 11 (steps ST50 to ST70).

For example, the gantry control circuit 25 controls the support column drive device 27 according to an instruction from the user via the input device 57, and adjusts the position of the gantry main body 11 so that the FOV includes the imaging portion. Examples of the imaging site of the subject P include sites of clinical interest in the internal structure during walking, such as ankles, toes, and soles. In the present embodiment, since the imaging portion actively moves, it is preferable that the gantry main body 11 is positioned so that the FOV includes the moving range of the imaging portion.

When the gantry main body 11 is positioned, the gantry control circuit 25 controls the rotation drive device 23 to rotate the rotation frame 21 around the central axis R1 at the set gantry rotation speed.

When it is determined that the subject P is walking in the optimum walking cycle W_opt, the system control circuit 61 sends a scan start instruction to the gantry control circuit 25 by the operation of the input device 57 by the operator. Upon receiving the scan start instruction, the gantry control circuit 25 controls the high voltage generator 43 to intermittently generate X-rays from the X-ray tube 17 according to the set X-ray conditions. As a result, X-rays are exposed for each segment corresponding to the specific phase of the walking cycle W_opt (step ST50). At this time, the rotating frame 21 rotates, but the gantry main body 11 is stationary. The X-rays generated from the X-ray tube 17 pass through the imaging site of the subject P and are intermittently detected by the X-ray detector 19, and the raw data on the X-rays detected by the X-ray detector 19 is obtained. It is intermittently collected by the data collection circuit 45 (step ST60). The collected raw data is transmitted to the image reconstruction device 51 by the non-contact data transmission device.

Hereinafter, the processes of steps ST50 to ST60 are repeatedly executed until all segments are exposed to X-rays (ST70).

During such processing of steps ST50 to ST70, for example, as shown in FIGS. 7 to 10, each time the X-ray tube 17 rotates around the subject P with respect to the subject P walking in the walking cycle W_opt. X-rays are exposed for S seconds (t = 0 to S, t = W_opt to W_opt + S, t = 2W_opt to 2W_opt + S, ...). At this time, the X-ray tube 17 exposes X-rays to each segment corresponding to the specific phase of the walking cycle W_opt.

Supplementally, as shown in FIG. 11A, the segments 0 to 7 facing the X-ray tube 17 change periodically according to the rotation of the X-ray tube 17 having a rotation speed R around the subject P. Then. This situation is shown in FIG. 11B in chronological order. That is, it progresses to the right from "Segment 2" shown at the upper left end, and when it reaches the right end, it moves to the left end of the line below by one line and proceeds to the right in the same way, and repeats the process, which is shown at the lower right end. The state up to segment 1 ”is shown in chronological order. The length of one row (9 columns) of this time series corresponds to the walking cycle W_opt (= R + S). Each column of the time series shows the segments corresponding to the same phase in the walking cycle W_opt. The number of rows in the time series (8 rows) is the same as the number of segments (8), that is, the number of walking cycles required for reconstructing one image (8 times). As a result, as shown by the broken line in FIG. 11B, it can be seen that X-rays are exposed to each segment in a predetermined same phase, and the raw data of all the segments are collected in this same phase. This is not limited to the case of the walking cycle W_opt = R + S, and is the same as long as the walking cycle W_opt is an odd multiple of the X-ray exposure time S. For example, even when W_opt = R + 3S, as shown by the broken line in FIG. 12, although the order of the segments is different from that in FIG. 11 (b), X-rays are exposed to each segment in a predetermined same phase, and the same Raw data for all segments is collected in phase.

In any case, when the exposure of X-rays to all the segments is completed, the gantry control circuit 25 controls the rotation drive device 23, the support column drive device 27, the equipment control circuit 39, and the high voltage generator 43, and X-rays. End CT imaging.

After the end of step ST70, the image reconstruction apparatus 51 reconstructs the CT image by segment reconstruction processing based on the raw data collected in step ST60 (step ST80). For example, the image reconstructing device 51 reconstructs a CT image of a predetermined phase based on raw data collected from all segments. The predetermined phase can be arbitrarily set by the user via the input device 57. The CT image may be reconstructed as two-dimensional slice data or as three-dimensional volume data. The CT image is stored in the main memory circuit 59 in association with the phase.

After that, the system control circuit 61 displays the reconstructed CT image on the display device 55 (step ST90). For example, a CT image relating to a predetermined phase of gait dynamics is displayed as a still image. When the CT image is volume data, the image processing device 53 performs three-dimensional image processing on the volume data to generate a two-dimensional image, and the two-dimensional image is displayed on the display device 55. When the CT image is slice data, the image processing device 53 performs gradation processing, noise reduction processing, or the like on the slice data to generate a two-dimensional image, and the two-dimensional image is displayed on the display device 55. The CT image displayed on the display device 55 is used for the diagnosis of the user. By observing the displayed CT image, it is possible to grasp the internal structure of the local range of the subject P (for example, the imaging site including the knee joint and the like) during walking.

As described above, according to the present embodiment, the dynamic cycle of the subject is measured, the imaging conditions of the subject are set based on the dynamic cycle, and the optimum dynamic cycle of the subject is acquired based on the imaging conditions. Then, the acquired dynamic cycle is notified to the subject. This makes it possible to capture periodic dynamics even when there is no stationary phase.

Supplementally, after measuring the basic walking cycle W_measure of the subject P, the walking cycle W_opt that minimizes the time resolution is calculated from the relationship between the basic walking cycle W_measure and the gantry rotation speed R, and the walking cycle W_opt is set to a treadmill or the like. The measurement / notification device 29 notifies the subject P. Subject P walks so as to maintain the notified walking cycle W_opt. Thereby, the walking dynamics of the subject P can be adjusted to the walking cycle W_opt. Therefore, by exposing the segments to X-rays in the same phase of the gait dynamics and reconstructing the projection data of each segment, it is possible to capture the periodic dynamics even when there is no stationary phase.

The first embodiment may be modified as in the following first modification or second modification.

The first modification omits the measurement of the basic walking cycle of the subject, and can be applied when, for example, the basic walking cycle can be known to some extent from the age, sex, and physique of the subject. Specifically, as shown in the flowchart of FIG. 13, in the first modification, instead of steps ST10 to ST20 relating to measurement, step ST20A for setting shooting conditions without measuring the dynamic cycle is executed. .. In this step ST20A, the operation console 52 sets the shooting conditions by the operation of the operator. The shooting conditions to be set may be preset default values or values determined by the operator. That is, in step ST20A, the imaging conditions in step ST20 are set without measuring the dynamic cycle of the subject P. When step ST20A is executed, subsequent ST30 to ST90 are executed in the same manner as described above. That is, in the first modification, the imaging conditions of the subject P are set without measuring the dynamic cycle of the subject P (eg, the basic walking cycle), and the optimum dynamics of the subject P are set based on the imaging conditions. The cycle is acquired and the optimum dynamic cycle is notified to the subject P. As such a first modification, for example, when the difference between the basic walking cycle of the subject P and the optimum walking cycle W_opt of the subject P is equal to or less than a predetermined reference value, the first embodiment The same effect as

As shown in the flowchart of FIG. 14, the second modification is a modification of the first modification, and instead of step ST40, step ST40A (steps ST41A to ST43A) accompanied by measurement and modification of the dynamic cycle is executed. To do.

For example, in step ST41A, the dynamic cycle (eg, walking cycle W_measure) of the subject P is measured in the same manner as in step ST10 described above.

In step ST42A, the optimum dynamic cycle is modified according to the difference between the measured dynamic cycle and the optimum dynamic cycle (eg, walking cycle W_opt) acquired in step ST30. For example, when the difference between the two is larger than a predetermined reference value, the parameter A is modified so as to satisfy the equation (2) based on the measured walking cycle W_measure. When the parameter A is modified, the gantry rotation speed R used in the equation (2) may be the current gantry rotation speed R or the modified gantry rotation speed R. In any case, the optimum walking cycle W_opt is recalculated by the equation (1) using the modified parameter A. After that, the walking cycle W_opt acquired in step ST30 is corrected to the walking cycle W_opt recalculated in step ST42A.

In step ST43A, the modified optimum walking cycle W_opt is notified to the subject P in the same manner as in step ST40 described above.

As such a second modification, the same effect as that of the first embodiment can be obtained.

<Second embodiment>
FIG. 15 is a schematic view showing a schematic configuration of an X-ray computed tomography apparatus according to a second embodiment. Now, I will mainly describe the different parts. Duplicate description will be omitted for each of the following embodiments in the same manner.

That is, the second embodiment is a modified example of the first embodiment, and as shown in FIG. 4, in a modified configuration including the measuring device 29a and the notification device 29b, some specific examples of the notification device 29b. Is shown.

Here, as the notification device 29b, for example, as shown in FIG. 15, a laser floodlight 29b1, a display 29b2, or a speaker 29b3 can be used to notify the dynamic cycle of the subject P.

The laser floodlight 29b1 is controlled by the device control circuit 39, and irradiates the feet of the subject P with light to notify the location and timing of the feet. Note that the notification by light is not limited to the laser floodlight 29b1, and may be realized, for example, by arranging a plurality of LEDs under a transparent protective plate provided on the floor and causing these LEDs to emit light. That is, as the notification device 29b, any device can be applied as long as it is a device that illuminates the feet of the subject P when notifying by light.

The display 20b2 is a device controlled by the device control circuit 39 and displaying information related to the dynamic cycle on the screen. For example, the display 20b2 is attached to the front surface of the gantry and notifies the timing of foot down by the display screen.

The speaker is a device that is controlled by the device control circuit 39 and outputs a voice related to the dynamic cycle to notify the dynamic cycle. Notify.

Even with the above configuration, the optimum dynamic cycle can be notified to the subject, so that the same effect as that of the first embodiment can be obtained.

<Third embodiment>
16 and 17 are schematic views showing an example of a schematic configuration of the X-ray computed tomography apparatus according to the third embodiment.

The third embodiment is a modification of the first embodiment, the first modification, or the second modification. Specifically, during the operation of the first embodiment or the like, the location and height of the foot during walking are checked, and if the foot deviates from a certain range, the exposure of the cycle is stopped and the photograph cannot be taken. The cycle is taken again at the end of the scan.

Along with this, in the third embodiment, as shown in FIG. 4, some specific examples of the measuring device 29a can be used in the modified configuration including the measuring device 29a and the notification device 29b. As the measuring device 29a, for example, as shown in FIG. 16, the line sensor 29a3 may be arranged so as to face each other below the two columns 13. As the line sensor 29a3, for example, an infrared sensor including a plurality of light emitting elements arranged in one direction and a light receiving element that receives infrared rays emitted from each light emitting element can be used. According to the infrared sensor, the location and height of the foot of the subject P can be detected based on the passage and blocking state of infrared light between the two elements. The arrangement direction of the light emitting elements may be either a direction substantially parallel to the direction in which the subject P walks or a direction substantially perpendicular to the walking direction.

Further, for example, as the measuring device 29a, as shown in FIG. 17, a plurality of cameras 29a4 may be arranged toward the foot of the subject P. A plurality of markers 29a5 are attached to the feet of the subject P. Such a plurality of cameras 29a4 can detect the location and height of the foot of the subject P by photographing the plurality of markers 29a5.

Alternatively, the X-ray computed tomography apparatus may detect the disturbance of the location and height of the subject P from the CT value of the CT image when synchronization is not applied.

Next, the operation of the X-ray computed tomography apparatus configured as described above will be described with reference to the flowchart of FIG.

Now, it is assumed that the subject P is walking on the treadmill during the execution of step ST40 or step ST40A as described above. In this state, the above-mentioned steps ST50 to ST70 are repeatedly executed.

However, in the present embodiment, steps ST100 (steps ST110 to ST150) for checking the location and height of the foot of the subject P are executed before the X-ray exposure by step ST50.

First, the dynamics of the subject P are measured by the measuring device 29a, and the measurement result is sent to the system control circuit 61 via the device control circuit 39 and the gantry control circuit 25.

In step ST110, the system control circuit 61 determines whether or not the dynamics of the subject P indicated by the measurement result is within the predetermined range, and if it is within the predetermined range, the process proceeds to step ST50 described above. If not, the system control circuit 61 controls the gantry control circuit 25 to stop the X-ray exposure by the X-ray tube 17 (step ST120), and records the segment in which the exposure is stopped (step ST130). ). Subsequently, the system control circuit 61 waits until the dynamics of the subject P recovers within a predetermined range. Specifically, the system control circuit 61 repeatedly executes step ST140 for determining whether or not the dynamics of the subject P is within a predetermined range. As a result of the determination in step ST140, when the dynamics of the subject P recovers within a predetermined range, the gantry control circuit 25 is made to execute the restart process (step ST150).

The restart process may be any of the following (i) to (iii), for example. That is, (i) the gantry control circuit 25 may wait until it reaches the same specific phase as the specific phase of the segment recorded in step ST130, and restart the exposure when the same specific phase is reached. For example, in the time series shown in FIG. 11B, when the segment 3 of the column shown by the broken line is recorded, the time series proceeds in the same manner as described above, and the segments 4, 5, 6 and 7 of the column shown by the broken line are recorded. It is assumed that the exposure is completed and the lower right end is reached. Subsequently, the time series may move from the lower right end to the upper left end, proceed in the same manner as described above, and resume the exposure when the segment 3 in the column indicated by the broken line is reached again.

(Ii) When the dynamics of the subject P deviates from the predetermined range, the gantry control circuit 25 notifies the subject to accelerate the walking cycle via the device control circuit 39 and the notification device 29b, and the gantry rotation speed R You may be able to catch up with. As a notification for accelerating the walking cycle, for example, a message such as "Please skip" may be displayed as an image or output as a voice.

(Iii) When the dynamics of the subject P deviates from the predetermined range, the gantry control circuit 25 temporarily increases the gantry rotation speed R so that the gantry control circuit 25 has the same specific phase as the specific phase of the segment recorded in step ST130. Exposure may be resumed at that point.

After the end of step ST150, the system control circuit 61 shifts to step ST110. In step ST110, if the dynamics of the subject P are restored within a predetermined range, the process proceeds to step ST50 described above.

Hereinafter, steps ST50 to ST70 are executed in the same manner as described above. However, in step ST70, at the end of the scan, it is determined whether or not there is a segment recorded in step ST130, and if there is a recorded segment, a step is performed until steps ST50 to ST60 are executed in the segment. Does not shift to ST80. When steps ST50 to ST60 are executed in the segment, the recording in step ST130 is invalidated, and step ST70 shifts to step ST80.

Hereinafter, steps ST80 to ST90 are executed in the same manner as described above.

As described above, according to the present embodiment, in CT imaging, it is determined whether or not the dynamics of the subject is within a predetermined range, and if not, the X-ray exposure is stopped. In addition to the effect of the above embodiment, it is possible to reduce unnecessary exposure when the dynamics of the subject deviate.

<Fourth Embodiment>
FIG. 19 is a schematic diagram for explaining the X-ray computed tomography apparatus according to the fourth embodiment. In FIG. 19, the columns 13 and the like are not shown.

The fourth embodiment is a modification of the second embodiment, in which the bending and stretching of the elbow of the subject P is imaged by X-ray CT in a configuration using the display 29b2 as the notification device 29b.

That is, the movement that is the target of CT imaging is not limited to walking. The motion of periodically bending and stretching the elbow according to the optimum dynamic cycle notified from the display screen of the display 29b2 is also targeted. That is, the X-ray computed tomography apparatus is not limited to the standing CT apparatus, and may be a normal CT apparatus (a lying CT apparatus).

Even with the above configuration, the optimum dynamic cycle (eg, elbow bending / stretching cycle) can be notified to the subject P, so that the same effect as that of the second embodiment can be obtained.

According to at least one embodiment described above, the optimum dynamic cycle of the subject is acquired, and the acquired dynamic cycle is notified to the subject. This makes it possible to capture periodic dynamics even when there is no stationary phase.

Although some embodiments of the present invention have been described, these embodiments are presented as examples 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 changes can be made without departing from the gist of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, as well as in the scope of the invention described in the claims and the equivalent scope thereof.

10 ... gantry device, 11 ... gantry body, 13 ... support, 15 ... opening, 17 ... X-ray tube, 19 ... X-ray detector, 21 ... rotating frame, 23 ... rotating drive device, 25 ... gantry control circuit, 27 ... Prop drive device, 29 ... measurement / notification device, 29a ... measurement device, 29b ... notification device, 39 ... device control circuit, 41 ... operating condition storage circuit, 43 ... high voltage generator, 45 ... data acquisition circuit, 51 ... image Reconstructor, 52 ... Operator, 53 ... Image processing device, 55 ... Display device, 57 ... Input device, 59 ... Main storage circuit, 61 ... System control circuit, 511 ... Preprocessing unit, 513 ... Projection data storage unit, 515 ... Reconstruction calculation unit.

Claims (6)

A mount that can scan the subject and
A walking control unit including a support unit that supports the subject, a measurement unit that measures the walking state of the subject, and a drive unit that drives the support unit to encourage walking of the subject.
A setting means for setting imaging conditions of the subject based on the walking state measured by the measuring unit, and
An acquisition means for acquiring the optimum walking cycle of the subject during scanning of the subject based on the imaging conditions, and
A control means for controlling the drive unit so as to encourage the subject supported by the support unit to walk in the optimum walking cycle.
An X-ray computed tomography apparatus comprising. The X-ray computed tomography apparatus according to claim 1, further comprising a reconstruction means for generating a reconstruction image by a segment reconstruction process using raw data of a plurality of segments collected by the scan. Corrective measures and
Further equipped with notification means,
The measuring unit measures the walking cycle as the walking state, and measures the walking cycle.
It said modifying means modifies said optimum walking cycle in response to a difference between said optimal gait cycle the measured walking cycle,
The notification means, the optimal gait cycle notifies the subject, when the optimum walking cycle is modified, notifies the modified gait cycle to the subject,
The X-ray computed tomography apparatus according to claim 1. The X-ray computed tomography apparatus according to claim 3, wherein the measuring unit measures the walking cycle of the subject using an optical camera or a pressure sensor. The X-ray computed tomography apparatus according to claim 3, wherein the notification means uses a laser to notify the walking cycle of the subject. The X-ray computed tomography apparatus according to claim 3, wherein the notification means notifies the walking cycle by displaying information related to the walking cycle on a screen or outputting a voice related to the walking cycle.

Images