JP7780912B2 - X-ray computed tomography apparatus and gantry - Google Patents

Description

The embodiments disclosed in this specification and drawings relate to an X-ray computed tomography apparatus and a gantry device.

Conventionally, the gantry for an X-ray computed tomography apparatus has a rotating frame on which various units are mounted. These units (e.g., X-ray tubes) can generate heat when the X-ray computed tomography apparatus is in operation. To prevent these units from failing due to heat, these units must be cooled. For this reason, openings are provided on the side of the rotating frame parallel to its rotation axis to provide a flow path for air that has cooled the various units.

The air that has cooled the various units flows out (exhaust) from openings on the rotating frame to the outside in the radial direction of the rotating frame (hereinafter referred to as the radially outward direction) as the rotating frame rotates. The airflow flowing out from the openings collides with the tip of the support frame that faces the rotating frame and supports it. At this time, a noise (also known as narrowband noise or peak noise) that is harsh to the subject and/or user is generated at a frequency related to the rotational speed of the rotating frame and the airflow flowing out from the openings.

Completely closing the opening prevents air from flowing out of the opening, thereby suppressing the generation of the noise. However, completely closing the opening blocks the cooling intake and exhaust flow paths to the various units mounted on the rotating frame. This prevents the various units from being adequately cooled, which could result in malfunctions of the units.

Japanese Patent Application Laid-Open No. 2007-151616

One of the problems that the embodiments disclosed in this specification and drawings attempt to solve is to reduce noise while maintaining the cooling function for the various units mounted on the rotating frame. However, the problems that the embodiments disclosed in this specification and drawings attempt to solve are not limited to the above problem. Problems corresponding to the effects of each configuration shown in the embodiments described below can also be positioned as other problems.

The X-ray computed tomography apparatus according to this embodiment includes a rotating frame and a support frame. An X-ray tube that generates X-rays is attached to the rotating frame. The support frame supports the rotating frame so that it can rotate around a rotation axis along a predetermined rotation direction. The rotating frame has at least one opening in a surface along the rotation axis. At least one of a first edge of the opening on the rotation direction side and a second edge of the opening on the opposite side to the rotation direction is non-parallel to the rotation axis.

FIG. 1 is a diagram showing an example of the arrangement of an X-ray CT apparatus according to an embodiment. FIG. 2 is a perspective view showing an example of the gantry device from which an exterior cover is removed according to the embodiment; 3A and 3B are diagrams showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of the acoustic power level depending on the angle of the corner of the opening in the embodiment; FIG. 4 is a diagram showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of the acoustic power level depending on the angle of the corner of the opening, according to the embodiment. 5A and 5B are diagrams showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of the acoustic power level depending on the angle of the corner of the opening in the embodiment; FIG. 6 is a diagram showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of acoustic power level according to the angle D between a first corner and a second corner of the opening, according to an embodiment. FIG. 7 is a diagram showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of acoustic power level according to the angle between a first corner and a second corner of the opening, in the embodiment. FIG. 8 is a diagram showing an example of the shape of an opening provided on a side surface of a rotating frame and an example of a change in the relative value of acoustic power level according to the angle between a first corner and a second corner of the opening, in the embodiment. FIG. 9 is a diagram showing an example of airflow (indicated by arrows) flowing out from a rectangular opening according to a comparative example of the embodiment. FIG. 10 is a schematic diagram illustrating a comparative example of the embodiment, showing how air currents A and B collide with the leading edge of the frame as the rotating frame rotates. 11 is a diagram showing an example of airflow A and airflow B at an opening corresponding to FIG. 6 according to the embodiment. FIG. 12 is a diagram showing an example of changes in pressure at the tip of the frame in the embodiment and a comparative example. 13 is a diagram showing an example of the shape of the opening and the tip corner at the tip of the frame shown in FIG. 6 according to a modified example of the embodiment, and an example of the change in the relative value of the acoustic power level depending on the angle of the tip corner at the tip of the frame. 14 is a diagram showing an example of the shape of the opening and the tip corner at the tip of the frame shown in FIG. 5 according to a modified example of the embodiment, and an example of the change in the relative value of the acoustic power level depending on the angle of the tip corner at the tip of the frame.

Hereinafter, with reference to the drawings, an embodiment of an X-ray computed tomography apparatus (hereinafter referred to as an X-ray CT (computed tomography) apparatus) and a gantry will be described in detail. In the following embodiments, parts with the same reference numerals perform similar operations, and duplicate descriptions will be omitted where appropriate.

(Embodiment)
FIG. 1 is a diagram showing an example of the configuration of an X-ray CT system 1 according to this embodiment. As shown in FIG. 1, the X-ray CT system 1 includes, for example, a gantry 10, a bed 30, and a console 40. In this embodiment, the rotation axis of the rotating frame 13 in a non-tilted state or the longitudinal direction of the table 33 of the bed 30 is defined as the Z-axis direction, the axis perpendicular to the Z-axis direction and horizontal to the floor surface is defined as the X-axis direction, and the axis perpendicular to the Z-axis direction and perpendicular to the floor surface is defined as the Y-axis direction. For convenience of explanation, multiple gantry devices 10 are depicted in FIG. 1, but the actual configuration of the X-ray CT system 1 includes only one gantry device 10.

The gantry device 10 and the bed device 30 operate based on user operations via the console device 40, or via an operation unit provided on the gantry device 10 or the bed device 30. The gantry device 10, the bed device 30, and the console device 40 are connected to each other via wire or wirelessly so that they can communicate with each other.

Figure 2 is a perspective view showing an example of a gantry 10 with its exterior cover removed. The gantry 10 is an apparatus having an imaging system that irradiates a subject P with X-rays and collects projection data from the detected X-rays that have passed through the subject P. As shown in Figures 1 and 2, the gantry 10 includes a support frame, an X-ray tube 11 (X-ray generator), an X-ray detector 12, a rotating frame 13, an X-ray high-voltage device 17, a control device 18, a collimator 19, a wedge 20, and a DAS (Data Acquisition System) 21. The support frame supports the rotating frame 13 so that it can rotate around a rotation axis (Z-axis) in a predetermined direction. The support frame includes a fixed frame 5, a pair of standing frames 6, a base stand 7, and two gantry arms 8.

As shown in Figure 2, the fixed frame 5 supports the rotating frame 13 rotatably around the rotation axis R1 via bearings. The fixed frame 5 is a metal frame made of a metal such as aluminum with a bore (opening) formed in the center. The fixed frame 5 supports the rotating frame 13 rotatably around the rotation axis R1 (Z-axis) via bearings (hereinafter referred to as support bearings). A pair of standing frames 6 are attached to both side surfaces of the fixed frame 5 via platform arms 8.

A base stand 7 is attached to the other end of the pair of standing frames 6. A pair of standing frames 6 are erected on the base stand 7. The base stand 7 is installed on the floor of the examination room SR. The base stand 7 supports the fixed frame 5 via the standing frames 6, spaced apart from the floor. The base stand 7 is made of a metal such as aluminum.

Two gantry arms 8 support the fixed frame 5 so that they can tilt around a horizontal axis (X-axis) R2 that is perpendicular to the rotation axis R1 and parallel to the floor. Each gantry arm 8 is attached to the top of the base stand 7, connecting the base stand 7 to the fixed frame 5. Tilting the fixed frame 5 causes a vertical axis R3 that is perpendicular to the rotation axis R1 and the horizontal axis R2 to tilt relative to the floor. The gantry arms 8 tilt the fixed frame 5 in response to a drive signal supplied from a drive unit (not shown). The gantry arms 8 are made of metal such as aluminum. The side of the rotating frame 13 on which the X-ray tube 11 and other components are attached is referred to as the front side, and the side facing the fixed frame 5 is referred to as the back side. The tip 15 of the gantry arm 8, in other words, the tip of the support frame facing the rotating frame 13 (hereinafter referred to as the frame tip) 15, is close to the rotating frame 13 without contacting it.

The X-ray tube 11 is a vacuum tube that generates X-rays by irradiating thermions from a cathode (filament) toward an anode (target) through the application of high voltage and filament current from the X-ray high-voltage device 17. X-rays are generated when thermions collide with the target. The X-rays generated at the tube focus of the X-ray tube 11 are shaped into a cone beam, for example, via a collimator 19, and irradiated onto the subject P. For example, the X-ray tube 11 may be a rotating anode type X-ray tube that generates X-rays by irradiating a rotating anode with thermions. Note that this embodiment can be applied to both single-tube X-ray CT devices and so-called multi-tube X-ray CT devices in which multiple pairs of X-ray tubes 11 and X-ray detectors 12 are mounted on a rotating frame 13.

The X-ray detector 12 detects X-rays emitted from the X-ray tube 11 and passing through the subject P, and outputs an electrical signal corresponding to the X-ray dose to the DAS 21. The X-ray detector 12 has, for example, multiple detector element rows in which multiple detector elements are arranged in the channel direction along a single arc centered on the focal point of the X-ray tube 11. The X-ray detector 12 has, for example, a structure in which multiple detector element rows are arranged in the slice direction (row direction).

The X-ray CT device 1 is available in two types: a rotate/rotate type (third-generation CT) in which the X-ray tube 11 and X-ray detector 12 rotate together around the subject P, and a stationary/rotate type (fourth-generation CT) in which a large number of X-ray detection elements are fixed in a ring-shaped array and only the X-ray tube 11 rotates around the subject P. Either type is applicable to this embodiment. For the sake of concreteness, the following description will use a third-generation CT as an example of the X-ray CT device 1 of this embodiment.

The X-ray detector 12 is, for example, an indirect conversion detector having a grid, a scintillator array, and a photosensor array. The scintillator array has multiple scintillators, each of which has scintillator crystals that output light with a photon quantity corresponding to the amount of incident X-rays. The grid is placed on the X-ray incident side of the scintillator array and has an X-ray shielding plate that functions to absorb scattered X-rays.

The grid is sometimes called a collimator (one-dimensional collimator or two-dimensional collimator). The photosensor array has the function of converting the amount of light from the scintillator into an electrical signal corresponding to the amount of light, and includes photosensors such as photomultiplier tubes (PMTs). The X-ray detector 12 may be a direct conversion type detector that has a semiconductor element that converts incident X-rays into an electrical signal. The X-ray detector 12 may also be a photon counting type X-ray detector. The X-ray detector 12 is an example of an X-ray detection unit.

The rotating frame 13 has a bore and is fitted with an X-ray tube 11 that generates X-rays. Specifically, the rotating frame 13 is a cylindrical frame that supports the X-ray tube 11 and X-ray detector 12 facing each other and rotates the X-ray tube 11 and X-ray detector 12 using a control device 18 (described below). The rotating frame 13 is rotatably supported on the fixed frame 5 via support bearings. The rotating frame 13 receives power from the drive mechanism of the control device 18 and rotates at a constant angular velocity around the rotation axis R1.

The rotating frame 13 has at least one opening on a surface along the rotation axis (Z-axis). That is, at least one opening is provided on the side surface of the rotating frame 13 that is parallel to the rotation axis (Z-axis). The installation position of the opening on the side surface of the rotating frame 13 is shown, for example, by IL in Figure 2. Note that the installation position of the opening is not limited to Figure 2 and can be changed as appropriate depending on the relative positional relationship with the various units mounted on the rotating frame 13. Furthermore, for example, if two openings are provided on the rotating frame 13, the openings are arranged, for example, at two installation positions facing each other with the rotation axis of the rotating frame 13 as the center of symmetry. The shape of the openings will be explained later.

In addition to the X-ray tube 11 and X-ray detector 12, the rotating frame 13 also supports an X-ray high-voltage device 17 and a DAS 21. The rotating frame 13 is housed in a roughly cylindrical housing with a bore that forms the imaging space. The central axis of the bore coincides with the rotation axis R1 of the rotating frame 13.

The detection data generated by the DAS 21 is transmitted, for example, by optical communication from a transmitter having a light-emitting diode (LED) to a receiver having a photodiode provided in a non-rotating portion of the gantry 10 (for example, the fixed frame 5), and then transferred to the console device 40. The method of transmitting the detection data from the rotating frame 13 to the non-rotating portion of the gantry 10 is not limited to the optical communication described above, and any method of non-contact data transmission may be used.

The X-ray high voltage device 17 has electrical circuits such as a transformer and rectifier, and includes a high voltage generator that generates the high voltage to be applied to the X-ray tube 11 and the filament current to be supplied to the X-ray tube 11, and an X-ray control device that controls the output voltage according to the X-rays emitted by the X-ray tube 11. The high voltage generator may be a transformer type or an inverter type. The X-ray high voltage device 17 may be provided on the rotating frame 13 or on the fixed frame 5 side of the gantry device 10.

The control device 18 has a processing circuit including a CPU (Central Processing Unit) and other components, and drive mechanisms such as motors and actuators. The processing circuit has hardware resources such as processors such as a CPU or MPU (Micro Processing Unit), and memory such as ROM (Read Only Memory) or RAM (Random Access Memory).

The control device 18 may also be implemented using an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), other complex programmable logic devices (CPLDs), or simple programmable logic devices (SPLDs). The control device 18 controls the X-ray high-voltage device 17, DAS 21, and other components in accordance with commands from the console device 40. The processor performs the above control by reading and executing programs stored in the memory.

The control device 18 also has the function of receiving input signals from the console device 40 or an input interface attached to the gantry device 10 and controlling the operation of the gantry device 10 and the bed device 30. For example, the control device 18 receives input signals and controls the rotation of the rotating frame 13, the tilt of the gantry device 10, and the operation of the bed device 30 and the tabletop 33.

The control of tilting the gantry 10 may be achieved by the control device 18 rotating the rotating frame 13 around the horizontal axis R2 based on inclination angle (tilt angle) information input via an input interface attached to the gantry 10. The control device 18 may be provided in the gantry 10 or in the console device 40. The control device 18 may be configured to directly incorporate the program into the circuitry of the processor, instead of storing the program in the memory. In this case, the processor achieves the above control by reading and executing the program incorporated into the circuitry.

The collimator 19 is a lead plate or the like that focuses the X-rays that have passed through the wedge 20 into the X-ray irradiation range, and forms a slit by combining multiple lead plates or the like.

The wedge 20 is a filter used to adjust the amount of X-rays emitted from the X-ray tube 11. Specifically, the wedge 20 is a filter that transmits and attenuates the X-rays emitted 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. The wedge 20 is, for example, a wedge filter or bow-tie filter, and is a filter made of processed aluminum to have a predetermined target angle and thickness.

The DAS 21 has an amplifier that amplifies the electrical signals output from each X-ray detection element of the X-ray detector 12, and an A/D converter that converts the electrical signals into digital signals, generating detection data. The detection data generated by the DAS 21 is transferred to the console device 40. The DAS 21 is also an example of a data acquisition unit.

The bed device 30 is a device on which the subject P to be scanned is placed and moved, and is equipped with a base 31, a bed drive device 32, a top 33, and a top support frame 34. The base 31 is a housing that supports the top support frame 34 so that it can move vertically. The bed drive device 32 is a motor or actuator that moves the top 33, on which the subject P is placed, in the longitudinal direction of the top 33. The bed drive device 32 moves the top 33 under control of the console device 40 or the control device 18. The top 33, which is provided on the upper surface of the top support frame 34, is a plate on which the subject P is placed. Note that the bed drive device 32 may move the top support frame 34 in addition to the top 33 in the longitudinal direction of the top 33.

The console device 40 has a memory 41, a display 42, an input interface 43, and a processing circuit 44. Data communication between the memory 41, the display 42, the input interface 43, and the processing circuit 44 is performed via a bus (BUS).

Memory 41 is a storage device such as an HDD (Hard Disk Drive), SSD (Solid State Drive), or integrated circuit storage device that stores various information. Memory 41 stores, for example, projection data and reconstructed image data. In addition to an HDD or SSD, memory 41 may also be a drive device that reads and writes various information to portable storage media such as CDs (Compact Discs), DVDs (Digital Versatile Discs), and flash memory, or semiconductor memory elements such as RAM (Random Access Memory). The storage area of memory 41 may be located within the X-ray CT device 1 or in an external storage device connected via a network. Memory 41 also stores the control program related to this embodiment.

The display 42 displays various types of information. For example, the display 42 outputs medical images (CT images) generated by the processing circuitry 44, a GUI (Graphical User Interface) for receiving various operations from the operator, and the like. For example, the display 42 may be a liquid crystal display (LCD), a cathode ray tube (CRT), an organic electroluminescence display (OELD), a plasma display, or any other display, as appropriate. The display 42 may also be provided on the gantry device 10. The display 42 may also be a desktop type, or may be configured as a tablet terminal or the like capable of wireless communication with the console device 40 main body.

The input interface 43 accepts various input operations from the operator, converts the accepted input operations into electrical signals, and outputs them to the processing circuitry 44. For example, the input interface 43 accepts from the operator the acquisition conditions for acquiring projection data, the reconstruction conditions for reconstructing CT images, and the image processing conditions for generating post-processed images from CT images. As the input interface 43, for example, a mouse, keyboard, trackball, switch, button, joystick, touchpad, touch panel display, etc. can be used as appropriate.

In this embodiment, the input interface 43 is not limited to being equipped with physical operating components such as a mouse, keyboard, trackball, switch, button, joystick, touchpad, and touch panel display. For example, an example of the input interface 43 also includes an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs this electrical signal to the processing circuit 44. The input interface 43 may also be provided in the pedestal device 10. The input interface 43 may also be configured as a tablet terminal or the like that is capable of wireless communication with the console device 40 main body.

The processing circuitry 44 controls the overall operation of the X-ray CT system 1 in response to electrical signals of input operations output from the input interface 43. For example, the processing circuitry 44 has, as hardware resources, processors such as a CPU, MPU, and GPU (Graphics Processing Unit), and memories such as ROM and RAM. The processing circuitry 44 executes a system control function 441, a preprocessing function 442, and a reconstruction processing function 443 using a processor that executes programs deployed in memory.

The processing circuit 44, which executes the system control function 441, preprocessing function 442, and reconstruction processing function 443, respectively, corresponds to the system control unit, preprocessing unit, and reconstruction unit. Note that each of the functions 441 to 443 does not necessarily have to be realized by a single processing circuit. A processing circuit may also be configured by combining multiple independent processors, and each processor may execute a program to realize each of the functions 441 to 443.

The processing circuitry 44 controls each function of the processing circuitry 44 based on input operations received from the operator via the input interface 43 using the system control function 441. Specifically, the system control function 441 reads out a control program stored in the memory 41, expands it into the memory within the processing circuitry 44, and controls each part of the X-ray CT device 1 in accordance with the expanded control program. For example, the processing circuitry 44 controls each function of the processing circuitry 44 based on input operations received from the operator via the input interface 43.

The processing circuitry 44 uses the preprocessing function 442 to generate data by performing preprocessing such as logarithmic conversion, offset correction, inter-channel sensitivity correction, and beam hardening correction on the detection data output from the DAS 21. The data before preprocessing is referred to as raw data, and the data after preprocessing is referred to as projection data.

The processing circuitry 44 uses the reconstruction processing function 443 to perform reconstruction processing using filtered back projection (FBP) or iterative reconstruction, etc., on the projection data generated by the preprocessing function 442 to generate CT image data. The reconstruction processing function 443 stores the reconstructed CT image data in the memory 41.

The shape of the opening in the X-ray CT device 1 according to this embodiment, which is configured as described above, will now be described. The edge of the opening on the rotational direction side (hereinafter referred to as the first edge) has a shape such that the timing of collision between the airflow passing through the opening from the inside of the rotating frame 13 to the outside of the rotating frame 13 (hereinafter referred to as the passing airflow) and the frame tip 15 facing the rotating frame 13 is shifted in the circumferential direction of the rotating frame 13.

For example, at least one of the first edge and the edge of the opening opposite the rotation direction of the rotating frame 13 (hereinafter referred to as the second edge) is non-parallel to the rotation axis (Z-axis). For example, the first edge and the second edge are continuously inclined with respect to the rotation axis (Z-axis). Furthermore, the first edge has a first corner in the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. Note that the apex of the first corner of the first edge may be located in the center of the opening with respect to the direction of the rotation axis.

Figure 3 shows an example of the shape of an opening 13A provided on the side of the rotating frame 13, and an example of the change in the noise intensity level relative value (NIR) depending on the angle A of a first corner CA of the opening 13A. As shown in Figure 3, the first edge of the opening 13A is non-parallel to the rotation axis (Z-axis) and is continuously inclined with respect to the rotation axis (Z-axis). The first edge of the opening 13A has a first corner CA in the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. In Figure 3, the angle of the first corner CA is indicated by A. The apex of the first corner CA of the first edge of the opening 13A is located in the center of the opening 13A with respect to the direction of the rotation axis.

The acoustic power level relative value NIR is the relative noise intensity based on a conventional shape in which the opening shape is rectangular and the edge of the frame tip 15 (hereinafter referred to as the frame tip edge) is parallel to the rotation axis. The noise intensity NI of the conventional shape and the noise intensity NI' related to the opening 13A are calculated, for example, from the change in gas pressure over time obtained by computational fluid dynamics (CFD). The acoustic power level relative value NIR is calculated by taking the logarithm of the ratio between the noise intensity NI of the conventional shape and the noise intensity NI' related to the opening 13A.

When the opening 13A has a first edge as shown in Figure 3, the range AAR of angle A at the first corner CA, at which noise is reduced compared to the conventional shape, is a range from an angle exceeding 70° to an angle less than 180° (70° < A < 180°). As shown in Figure 3, at the lowest value of the acoustic power level relative value NIR, angle A is near 120°. Therefore, when angle A of the first corner CA of the first edge of the opening 13A is set near 120°, the noise reduction effect is maximized.

The second edge may have a shape that causes the timing of collision between the passing airflow and the frame tip 15 to be shifted relative to the circumferential direction of the rotating frame 13. For example, the second edge may be non-parallel to the rotation axis (Z-axis) and continuously inclined relative to the rotation axis (Z-axis). The second edge may also have a second corner relative to the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. The apex of the second corner of the second edge may be located in the center of the opening relative to the direction of the rotation axis.

Figure 4 shows an example of the shape of the opening 13B provided on the side of the rotating frame 13, and an example of the change in the acoustic power level relative value NIR depending on the angle B of the second corner CB of the opening 13B. As shown in Figure 4, the second edge of the opening 13B is non-parallel to the rotation axis (Z axis) and is continuously inclined with respect to the rotation axis (Z axis). Furthermore, the second edge of the opening 13B has a second corner CB with respect to the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. In Figure 3, the angle of the second corner CB is indicated by B. Furthermore, the apex of the second corner CB of the second edge of the opening 13B is located in the center of the opening 13B with respect to the direction of the rotation axis.

When the opening 13B has a second edge as shown in Figure 4, the range BAR of angle B at the second corner CB, at which noise is reduced compared to the conventional shape, is an angle range less than 120° (B<120°).

Figure 5 shows an example of the shape of an opening 13C provided on the side of the rotating frame 13, and an example of the change in the acoustic power level relative value NIR depending on the angle C of the second corner CC of the opening 13C. As shown in Figure 5, the second edge of the opening 13C is non-parallel to the rotation axis (Z-axis) and is continuously inclined with respect to the rotation axis (Z-axis). Furthermore, the second edge of the opening 13C has a second corner CC with respect to the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. In Figure 5, the angle of the second corner CC is indicated by C. Furthermore, the apex of the second corner CC of the second edge of the opening 13C is located in the center of the opening 13C with respect to the direction of the rotation axis.

When the opening 13C has a second edge as shown in Figure 5, the range of angles C CAR at the second corner CC at which noise is reduced compared to the conventional shape is an angle range of less than 120° (C<120°).

Furthermore, the first edge and second edge of the opening may have a shape such that the timing of collision between the passing airflow and the frame tip 15 is offset relative to the circumferential direction of the rotating frame 13. For example, the first edge and second edge of the opening are non-parallel to the rotation axis (Z-axis) and are continuously inclined relative to the rotation axis (Z-axis). In this case, the first edge has a first corner relative to the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. Note that the apex of the first corner of the first edge may be located in the center of the opening relative to the direction of the rotation axis (Z-axis).

The second edge also has a second corner in the circumferential direction of the rotating frame 13, i.e., the rotational direction of the rotating frame 13. The apex of the second corner of the first edge may be located in the center of the opening in the direction of the rotation axis (Z-axis).

Figure 6 shows an example of the shape of an opening 13D provided on the side of the rotating frame 13, and an example of the change in the acoustic power level relative value NIR depending on the angle D between the first corner CDF and the second corner CDR of the opening 13D. As shown in Figure 6, the first edge and second edge of the opening 13D are not parallel to the rotation axis (Z axis) and are continuously inclined with respect to the rotation axis (Z axis). Furthermore, the first edge of the opening 13D has a first corner CDF in the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13.

The second edge shown in FIG. 6 has a second corner CDR in the circumferential direction of the rotating frame 13, i.e., the rotational direction of the rotating frame 13. In FIG. 6, the angle between the first corner CDF and the second corner CDR is indicated by D. The apexes of the first corner CDF of the first edge and the second corner CDR of the second edge in the opening 13D are located in the center of the opening 13D in the direction of the rotation axis.

When the opening 13D has a first edge and a second edge as shown in FIG. 6, the range D of the first corner CDF and the second corner CDR, DAR, at which noise is reduced compared to the conventional shape, is an angle range of less than 120° (D<120°). Note that the first corner CDF and the second corner CDR may have different angles as long as they are both less than 120°.

Figure 7 shows an example of the shape of an opening 13E provided on the side of the rotating frame 13, and an example of the change in the acoustic power level relative value NIR according to the angle E between the first corner CEF and the second corner CER of the opening 13E. As shown in Figure 7, the first edge and second edge of the opening 13E are not parallel to the rotation axis (Z axis) and are continuously inclined with respect to the rotation axis (Z axis). Furthermore, the first edge of the opening 13E has a first corner CEF in the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13.

The second edge of the opening 13E has a second corner CER that is convex in the direction opposite to the rotation direction of the rotating frame 13. In Figure 7, the angle between the first corner CEF and the second corner CER is indicated by E. The apex of the first corner CEF of the first edge and the second corner CER of the second edge of the opening 13E is located in the center of the opening 13E with respect to the direction of the rotation axis.

When the opening 13E has a first edge and a second edge as shown in Figure 7, the range of angle E EAR at the first corner CEF and second corner CER, at which noise is reduced compared to the conventional shape, is an angle range of less than 120° (E < 120°). Note that the first corner CEF and second corner CER may have different angles as long as they are both less than 120°.

Figure 8 shows an example of the shape of an opening 13F provided on the side of the rotating frame 13, and an example of the change in the acoustic power level relative value NIR depending on the angle F between the first corner CFF and the second corner CFR of the opening 13F. As shown in Figure 8, the first edge and the second edge of the opening 13F are non-parallel to the rotation axis (Z axis) and are continuously inclined with respect to the rotation axis (Z axis). Furthermore, the first edge of the opening 13F has a first corner CFF in the circumferential direction of the rotating frame 13, i.e., the rotation direction of the rotating frame 13. The apex of the first corner CFF of the first edge of the opening 13F is located at a position offset along a predetermined direction of the rotation axis from the center of the opening 13F in the direction of the rotation axis.

The second edge of the opening 13F has a second corner CFR in the circumferential direction of the rotating frame 13, i.e., the rotational direction of the rotating frame 13. In Figure 8, the angle between the first corner CFF and the second corner CFR is indicated by F. The apex of the second edge at the second corner CER is located at a position offset from the center of the opening 13F in the direction of the rotation axis along the opposite direction to the specified direction.

When the opening 13F has a first edge and a second edge as shown in Figure 8, the range of angle F EAR between the first corner CFF and the second corner CFR, at which noise is reduced compared to the conventional shape, is an angle range of less than 80° (F<80°).

The X-ray CT device 1 according to the embodiment described above comprises a rotating frame 13 to which an X-ray tube 11 that generates X-rays is attached, and a support frame that supports the rotating frame 13 so that it can rotate around a rotation axis in a predetermined rotation direction. The rotating frame 13 has at least one opening on a surface along the rotation axis, and at least one of a first edge on the rotation direction side of the opening and a second edge on the opposite side of the rotation direction of the opening is non-parallel to the rotation axis. Furthermore, in the X-ray CT device 1 according to the embodiment, at least one of the first edge and the second edge is continuously inclined with respect to the rotation axis.

In the X-ray CT device 1 according to this embodiment, the first edge has a first corner portion in the circumferential direction of the rotating frame 13. In this X-ray CT device 1, the apex of the first corner portion is located in the center of the opening in the direction of the rotation axis. In this X-ray CT device 1, the angle of the first corner portion ranges from an angle exceeding 70° to an angle less than 180°.

In the X-ray CT device 1 according to the embodiment, the second edge has a second corner portion in the circumferential direction of the rotating frame 13. In the X-ray CT device 1, the apex of the second corner portion is located in the center of the opening in the direction of the rotation axis. In the X-ray CT device 1, the angle range of the second corner portion is less than 120°. In the X-ray CT device 1, the angle ranges of the first corner portion CDF and the second corner portion CDR are both less than 120°, and the angles of the first corner portion CDF and the second corner portion CDR may be different from each other. In the X-ray CT device 1, the second edge has a second corner portion CER that is convex in the direction opposite to the rotation direction of the rotating frame 13, and the apex of the second corner portion CER is located in the center of the opening in the direction of the rotation axis. In this case, the angle range of the first corner portion CEF and the angle range of the second corner portion CER are both less than 120°, and the angle of the first corner portion CEF and the angle of the second corner portion CER may be different from each other.

In the X-ray CT scanner 1 according to this embodiment, the apex of the first corner is located at a position offset from the center of the opening in the direction of the rotation axis along a predetermined direction of the rotation axis, and the apex of the second corner is located at a position offset from the center in the opposite direction to the predetermined direction. In addition, in this X-ray CT scanner 1, the range of the angle between the first corner and the second corner is an angle range of less than 80°.

Figure 9 shows, as a comparative example, an example of airflow (arrows: streamline vectors) flowing out from a rectangular opening AP. As shown in Figure 9, the airflow flows outward in the radial direction of the rotating frame (hereinafter referred to as the radially outward direction). Furthermore, when the rotating frame is rotating, i.e., when the X-ray computed tomography apparatus is operating, the airflow moves in the circumferential direction of the rotating frame 13 while flowing outward in the radially outward direction.

As shown in Figure 9, the airflow flowing out from the opening AP can be broadly divided into two types (airflow A and airflow B). Airflow A is the main type of airflow on the forward side of the opening AP in the direction of rotation. Airflow A flows in a generally radially outward direction relative to the outer circumferential surface of the rotating frame. Airflow B is the main type of airflow on the opposite side of the opening AP in the direction of rotation of the rotating frame. Although the airflow flowing out from the opening AP flows in a radially outward direction, this airflow moves along with the rotating frame RB. As a result, a negative pressure region is generated on the opposite side of the direction of rotation (hereinafter referred to as the counter-rotation side) of the airflow flowing out from the opening AP. Due to the effect of the negative pressure region, the airflow on the counter-rotation side of the opening AP flows in a radially outward direction and then is suddenly bent toward the negative pressure region generated on the counter-rotation side of the opening AP. As a result, airflow B becomes a large vortex at the back surface of the opening AP, as shown in Figure 9.

Figure 10 shows, as a comparative example, a schematic diagram illustrating airflow A and airflow B colliding with the frame tip FB as the rotating frame rotates. Airflow A and airflow B each cause very large pressure fluctuations when they collide with the frame tip FB. This generates aerodynamic noise due to fluid dynamics.

As shown in Figure 9, the shape of the conventional opening AP as a comparative example is a rectangle with sides approximately parallel to the rotation axis direction. Therefore, as shown in Figure 10, airflow A and airflow B are uniformly discharged from opening AP along the rotation axis direction and collide with the frame tip. In other words, for airflow A and airflow B, a series of airflows flowing radially outward along the rotation axis direction collide with the frame tip FB at the same time. This results in very large fluctuations in airflow pressure.

Note that these pressure fluctuations occur at a timing that depends on the rotation of the rotating frame RB. For this reason, noise caused by pressure fluctuations is classified as narrowband noise, which occurs at frequencies that are integer multiples of the rotation frequency of the rotating frame RB.

Figure 11 is a diagram showing an example of airflow A and airflow B at the opening 13D corresponding to Figure 6 in an embodiment. As shown in Figure 11, with the X-ray CT device 1 according to this embodiment, the timing at which airflow A and airflow B flowing out of the opening 13D collide with the frame tip 15 can be shifted in the direction of the rotation axis (Z axis). On the other hand, the streamlines of airflow A and the streamlines of the entrained airflow B in Figures 9 and 10 as comparative examples are uniformly aligned in the direction of the rotation axis. Therefore, in the comparative example, the energy of collision with the frame tip 15 is greater and the pressure fluctuations are also greater compared to this embodiment.

On the other hand, with the X-ray CT system 1 according to this embodiment, as shown in FIGS. 3 to 8, at least one of the first and second edges of the opening is continuously inclined with respect to the direction of the rotation axis so as to continuously shift the airflow streamline in the rotation direction. Figure 12 shows an example of pressure changes at the frame tip 15 in this embodiment and a comparative example. The pressure changes at the frame tip 15 are calculated, for example, by computational fluid dynamics (CFD). As shown in Figure 12, the pressure changes (pressure fluctuations) at the frame tip 15 in this embodiment are smaller than those in the comparative example. Therefore, with the X-ray CT system 1 according to this embodiment, pressure fluctuations can be kept smaller than those in the conventional comparative example, resulting in reduced noise.

As an application example of this embodiment, at least one of the first edge and second edge of the opening may have a stepped shape (step-like shape change) so that the timing of collision between the passing airflow and the frame tip 15 is shifted in the circumferential direction of the rotating frame 13. This application example achieves the same effects as this embodiment.

As a result of the above, the X-ray CT scanner 1 according to this embodiment can reduce noise while maintaining cooling performance without blocking the opening.

(Modification)
In this modification, the second edge of the opening has a terminal corner in the circumferential direction of the rotating frame 13, and the tip (frame tip 15) of the support frame facing the rotating frame 13 has a tip corner in the circumferential direction of the rotating frame 13 as a shape on the opposite side to the rotation direction. In this case, the terminal corner and the tip corner may be non-parallel to the rotation axis and continuously inclined with respect to the rotation axis. Furthermore, the apex of the tip corner may be located in the center of the opening with respect to the direction of the rotation axis.

Figure 13 shows an example of the shape of the opening 13D and the tip corner TC at the frame tip 15 shown in Figure 6, and an example of the change in the acoustic power level relative value NIR depending on the angle G of the tip corner TC at the frame tip 15. The second edge of the opening 13D shown in Figure 13 has a terminal corner EC in the circumferential direction of the rotating frame 13. As shown in Figure 13, the terminal corner EC and the tip corner TC are not parallel to the rotation axis and are continuously inclined with respect to the rotation axis. Also, as shown in Figure 13, the apex of the tip corner TC is located centrally with respect to the direction of the rotation axis. In Figure 13, the angle of the tip corner TC is indicated by G.

When the opening 13D has a first edge and a second edge as shown in FIG. 6, and the tip corner TC at the frame tip 15 has a shape as shown in FIG. 13, the range of angle G GAR at the tip corner TC at which noise is reduced compared to conventional shapes is a range of angles from greater than 60° to less than 180° (60°<G<180°). As shown in FIG. 13, at the lowest value of the acoustic power level relative value NIR, the angle G is near 120°. Therefore, when the angle G of the tip corner TC with respect to the opening 13D is set at near 120°, the noise reduction effect is maximized.

Figure 14 shows an example of the shape of the opening 13C and the tip corner TC at the frame tip 15 shown in Figure 5, and an example of the change in the acoustic power level relative value NIR depending on the angle H of the tip corner TC at the frame tip 15. In the opening 13C shown in Figure 14, the second edge has a terminal corner EC in the circumferential direction of the rotating frame 13. As shown in Figure 14, the first edge of the opening 13C is parallel to the rotation axis. On the other hand, the tip corner TC is not parallel to the rotation axis and is continuously inclined with respect to the rotation axis. Also, as shown in Figure 14, the apex of the tip corner TC is located in the center with respect to the direction of the rotation axis. In Figure 14, the angle of the tip corner TC is indicated by H.

When the opening 13C has a first edge and a second edge as shown in FIG. 5, and the tip corner TC at the frame tip 15 has a shape as shown in FIG. 14, the range of angle G HAR at the tip corner TC at which noise is reduced compared to conventional shapes is a range of angles from greater than 50° to less than 180° (50°<H<180°). As shown in FIG. 14, at the lowest value of the acoustic power level relative value NIR, the angle H is near 120°. Therefore, when the angle H of the tip corner TC with respect to the opening 13C is set at near 120°, the noise reduction effect is maximized.

In the X-ray CT device 1 according to the modified example described above, the second edge has a terminal corner EC in the circumferential direction of the rotating frame 13, and the third edge on the opposite side of the rotation direction at the frame tip 15 has a tip corner TC in the circumferential direction of the rotating frame 13. Furthermore, in this X-ray CT device 1, the terminal corner EC and tip corner TC are not parallel to the rotation axis and are continuously inclined relative to the rotation axis, with the apex of the tip corner TC being centered in the direction of the rotation axis.

Furthermore, in the X-ray CT device 1 according to the modified example, when the first edge is parallel to the rotation axis, the angle range of the tip corner TC is from an angle exceeding 50° to an angle less than 180°. Furthermore, in the present X-ray CT device 1, when the first edge and the second edge are not parallel to the rotation axis and are continuously inclined relative to the rotation axis, the angle range of the tip corner TC is from an angle exceeding 60° to an angle less than 180°.

The effects of this modified example are similar to those of the embodiment, so a detailed description will be omitted. Note that the shape of the opening in this modified example is not limited to the above description, and may be, for example, the shape of the opening shown in Figures 4, 7, and 8.

When the technical concepts of the embodiments are realized in a gantry 10, the gantry 10 comprises a rotating frame 13 to which an X-ray tube 11 that generates X-rays is attached, and a support frame that supports the rotating frame 13 so that it can rotate around a rotation axis in a predetermined rotation direction. The rotating frame 13 has at least one opening on a surface along the rotation axis, and at least one of the first edge on the rotation direction side of the opening and the second edge on the opposite side of the rotation direction of the opening is non-parallel to the rotation axis. The effects of the gantry 10 are similar to those of the embodiments, and therefore description thereof will be omitted.

At least the embodiments and variations described above can reduce noise while maintaining the cooling function for the various units mounted on the rotating frame 13.

While several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments may be embodied in a variety of other forms, and various omissions, substitutions, modifications, and combinations of embodiments may be made without departing from the spirit of the invention. These embodiments and their variations are included within the scope and spirit of the invention, as well as within the scope of the invention and its equivalents as set forth in the claims.

REFERENCE SIGNS LIST 1 X-ray CT device 5 Fixed frame 6 Standing frame 7 Base stand 8 Platform arm 10 Platform device 11 X-ray tube 12 X-ray detector 13 Rotating frame 13A, 13B, 13C, 13D, 13E, 13F Opening 15 Frame tip 17 X-ray high voltage device 18 Control device 19 Collimator 20 Wedge 21 DAS (Data Acquisition System)
30 Bed device 31 Base 32 Bed driving device 33 Top board 34 Top board support frame 40 Console device 41 Memory 42 Display 43 Input interface 44 Processing circuit 441 System control function 442 Preprocessing function 443 Reconstruction processing function

Claims (16)

a rotating frame on which an X-ray tube for generating X-rays is mounted;
a support frame that supports the rotating frame rotatably around a rotation axis in a predetermined rotation direction,
the rotating frame has at least one opening in a side surface of the rotating frame ;
At least one of a first edge on a front side of the opening in the rotation direction and a second edge on a rear side of the opening in the rotation direction is non-parallel to the rotation axis,
the first edge has a first corner portion that is convex toward the front side in the rotation direction;
X-ray computed tomography equipment. the first corner portion is located at the center of the width of the rotating frame in a direction perpendicular to the rotation direction in the opening portion;
2. The X-ray computed tomography apparatus according to claim 1 . the angle between the two sides forming the first corner is an angle included in the range of an angle exceeding 70° to an angle less than 180°;
3. The X-ray computed tomography apparatus according to claim 2 . a rotating frame on which an X-ray tube for generating X-rays is mounted;
a support frame that supports the rotating frame rotatably around a rotation axis in a predetermined rotation direction,
the rotating frame has at least one opening in a side surface of the rotating frame;
At least one of a first edge on a front side of the opening in the rotation direction and a second edge on a rear side of the opening in the rotation direction is non-parallel to the rotation axis,
the second edge has a second corner portion that is convex toward the rear side in the rotation direction ;
X- ray computed tomography equipment. the second corner portion is located at the center of the width of the rotating frame in a direction perpendicular to the rotation direction in the opening portion;
5. The X-ray computed tomography apparatus according to claim 4 . The angle between the two sides forming the second corner portion is an angle included in a range of angles less than 120°.
6. An X-ray computed tomography apparatus according to claim 5 . the first edge has a first corner portion that is convex toward the front side in the rotation direction,
The angle between the two sides forming the first corner portion is an angle less than 120°,
The angle between the two sides forming the second corner is an angle less than 120°,
an angle between the two sides forming the first corner portion and an angle between the two sides forming the second corner portion are different from each other;
6. An X-ray computed tomography apparatus according to claim 5 . the second edge has a second corner portion that is convex toward the rear side in the rotation direction ,
the first corner portion is located at a position offset along a predetermined direction of the rotation axis from a center of a width of the rotating frame along a direction perpendicular to the rotation direction in the opening,
the second corner portion is located at a position offset from the center along a direction opposite to the predetermined direction;
2. The X-ray computed tomography apparatus according to claim 1 . The angle between the two sides forming the first corner portion is an angle less than 80°,
The angle between the two sides forming the second corner portion is an angle less than 80°.
9. An X-ray computed tomography apparatus according to claim 8 . a rotating frame on which an X-ray tube for generating X-rays is mounted;
a support frame that supports the rotating frame rotatably around a rotation axis in a predetermined rotation direction,
the rotating frame has at least one opening in a side surface of the rotating frame;
At least one of a first edge on a front side of the opening in the rotation direction and a second edge on a rear side of the opening in the rotation direction is non-parallel to the rotation axis,
the support frame includes a fixed frame that supports the rotating frame rotatably about a rotation axis via a bearing, and a pair of base arms that support the fixed frame tiltably about a horizontal axis that is perpendicular to the rotation axis and parallel to a floor surface,
At the tip of the gantry arm , a third edge on the rear side in the rotation direction has a third corner portion that is convex toward the rear side in the rotation direction .
X- ray computed tomography equipment. the third corner portion is located at the center of the width of the pedestal arm along a direction perpendicular to the rotation direction ;
The X-ray computed tomography apparatus according to claim 10 . the first edge and the second edge are non -parallel to the rotation axis;
The angle between the two sides forming the third corner is an angle included in the range of an angle exceeding 60° to an angle less than 180°.
The X-ray computed tomography apparatus according to claim 1 1 . the first edge is parallel to the rotation axis, and the angle between the two sides forming the third corner is an angle included in the range of an angle exceeding 50° to an angle less than 180°;
The X-ray computed tomography apparatus according to claim 1 1 . the support frame includes a fixed frame that supports the rotating frame rotatably about a rotation axis via a bearing, and a pair of base arms that support the fixed frame tiltably about a horizontal axis that is perpendicular to the rotation axis and parallel to a floor surface,
When the rotating frame rotates,
The tip of the pedestal arm faces the opening,
an airflow passing through the opening from the inside of the rotating frame to the outside of the rotating frame collides with a tip of the pedestal arm ;
a timing at which the airflow collides with the tip of the pedestal arm is shifted relative to the direction of the rotation axis due to a shape of the first edge of the opening;
2. The X-ray computed tomography apparatus according to claim 1 . a rotating frame on which an X-ray tube for generating X-rays is mounted;
a support frame that supports the rotating frame rotatably around a rotation axis in a predetermined rotation direction,
the support frame includes a fixed frame that supports the rotating frame rotatably about a rotation axis via a bearing, and a pair of base arms that support the fixed frame tiltably about a horizontal axis that is perpendicular to the rotation axis and parallel to a floor surface,
the rotating frame has at least one opening in a side surface of the rotating frame;
At least one of a first edge on a front side of the opening in the rotation direction and a second edge on a rear side of the opening in the rotation direction is non-parallel to the rotation axis,
At least one of the first edge and the second edge has a stepped shape toward the front side in the rotation direction,
When the rotating frame rotates,
The tip of the pedestal arm faces the opening,
an airflow passing through the opening from the inside of the rotating frame to the outside of the rotating frame collides with a tip of the pedestal arm ;
a timing at which the airflow collides with the tip of the pedestal arm is shifted with respect to the direction of the rotation axis due to a shape of at least one of the first edge and the second edge of the opening ;
X- ray computed tomography equipment. a rotating frame on which an X-ray tube for generating X-rays is mounted;
a support frame that supports the rotating frame rotatably around a rotation axis in a predetermined rotation direction,
the rotating frame has at least one opening in a side surface of the rotating frame ;
At least one of a first edge on a front side of the opening in the rotation direction and a second edge on a rear side of the opening in the rotation direction is non-parallel to the rotation axis,
the first edge has a first corner portion that is convex toward the front side in the rotation direction;
Mounting device.