Radiographic apparatus, and temperature control method and temperature control program for radiographic apparatus

Abstract

To keep a detector at a constant temperature by cooling the detector more greatly in a radiographic apparatus, and a temperature control method and a program thereof.SOLUTION: A radiographic apparatus includes: a heat-conductive rotating plate to which a radiation source is fixed, and which rotates about a rotating shaft; and a radiation detector which includes a heat-conductive housing, and is fixed at a position facing the radiation source across the rotating shaft in the rotating plate partially with a gap from the rotating plate; and a heat dissipation mechanism which has a heat conductive material disposed in the gap for dissipating heat of the radiation detector to the rotating plate. In a state that a temperature of the radiation detector rises, the heat conductive material is moved from a non-contact position with the rotating plate or the radiation detector to a position where the radiation detector and the rotating plate are subjected to heat conduction.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a radiation imaging apparatus, a temperature control method for a radiation imaging apparatus, and a temperature control program. [Background technology]

[0002] In recent years, PCCT (Photon Counting Computed Tomography) devices, which are radiographic imaging devices equipped with photon-counting detectors, have become well known. Unlike the charge-integration detectors used in conventional CT (Computed Tomography) devices, photon-counting detectors are capable of counting the photons of incident radiation. Because PCCT devices can measure the energy of each photon, they can obtain more information than conventional CT devices.

[0003] In PCCT devices, incident photons are converted into electric charges in a semiconductor layer, and then counted by a photon-counting circuit. Such photon-counting detectors generate heat as they count photons. Because the characteristics of the photon-counting circuit change due to temperature changes caused by heat generation, various methods have been proposed to maintain a constant temperature for the detector.

[0004] For example, Patent Document 1 proposes a method for maintaining a constant temperature of a detector by forming an opening that can be opened and closed freely in the housing of the detector, acquiring information about the amount of heat generated by the detector, such as its temperature, and selectively opening and closing the opening based on the acquired information. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2024-037489 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in photon-counting detectors, heat generation from circuits such as photon-counting circuits provided in the detector is more significant than in conventional detectors, and therefore, the method described in Patent Document 1 alone may result in insufficient cooling of the detector.

[0007] The present disclosure has been made in consideration of the above circumstances, and aims to achieve a constant temperature for the detector by cooling the detector to a greater extent. [Means for solving the problem]

[0008] The radiation imaging apparatus according to the present disclosure includes: a thermally conductive rotating plate having a radiation source fixed thereto and rotating about a rotation axis; a radiation detector having a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis of the rotating plate with a partial gap therebetween; a heat dissipation mechanism having a thermally conductive material disposed in the gap for dissipating heat from the radiation detector to the rotating plate; In a situation where the temperature of the radiation detector rises, the thermally conductive material is moved from a position where it is not in contact with the rotating plate or the radiation detector to a position where it provides thermal conduction between the radiation detector and the rotating plate.

[0009] In the radiation imaging apparatus according to the present disclosure, the thermally conductive material comprises a first member and a second member having sliding surfaces inclined with respect to the surfaces of the rotating plate and the radiation detector facing each other, The first member may be fixed to the rotating plate or the radiation detector in the gap, the second member may be located away from the rotating plate or the radiation detector in an initial position, and when the temperature of the radiation detector rises, the second member may be moved to an operating position in which it slides relative to the first member and contacts the radiation detector or the rotating plate while maintaining contact with the first member.

[0010] In addition, in the radiation imaging apparatus according to the present disclosure, the heat dissipation mechanism includes a spring arranged along the radial direction of the rotating plate, one end of which is fixed to the rotating plate or the radiation detector, and the other end of which is located radially outward of the rotating plate relative to the one end and is fixed to the second member; The spring constant of the spring may be determined based on the angular velocity at which the rotary plate rotates, the position of the second member in the radial direction of the rotary plate, and the weight of the second member.

[0011] In addition, in the radiation imaging apparatus according to the present disclosure, the heat dissipation mechanism includes a drive unit having a motor and a ball screw whose one end is fixed to the motor and whose other end is screwed into the second member, The drive unit may drive a motor based on information relating to the amount of heat generated by the radiation detector, thereby moving the second member from the initial position to the operating position and from the operating position to the initial position.

[0012] In the radiation imaging apparatus according to the present disclosure, the information about the amount of heat generated may be a temperature measured by a temperature sensor provided in the radiation detector.

[0013] In the radiation imaging apparatus according to the present disclosure, the information about the amount of heat generated may be information based on a tube current applied to the radiation source.

[0014] In the radiographic imaging apparatus according to the present disclosure, the thermally conductive material is divided into a plurality of small members radially with respect to the rotation axis, The drive unit may change the positions and number of small members that provide thermal conduction between the radiation detector and the rotating plate, depending on at least one of the position at which the temperature rises in the radiation detector and the amount of heat generated.

[0015] The temperature control method for a radiation imaging apparatus according to the present disclosure includes: a rotating plate having thermal conductivity, a radiation source fixed thereto, and rotating about a rotation axis; a radiation detector having a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis of the rotating plate with a partial gap therebetween; A temperature control method for a radiographic imaging apparatus including a thermally conductive material disposed in a gap for dissipating heat from a radiation detector to a rotating plate, and a heat dissipation mechanism having a drive unit that moves the thermally conductive material from a position where it is not in contact with the rotating plate or the radiation detector to a position where the thermally conductive material is in thermal conduction between the radiation detector and the rotating plate when the temperature of the radiation detector rises, comprising: The computer obtains information about the heat generation of the radiation detector; Based on the information about the amount of heat generated, the driving of the heat conductive material by the driving unit is controlled.

[0016] The temperature control program for a radiation imaging apparatus according to the present disclosure includes: a rotating plate having thermal conductivity, a radiation source fixed thereto, and rotating about a rotation axis; a radiation detector having a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis of the rotating plate with a partial gap therebetween; A temperature control program that causes a computer to execute a temperature control method for a radiation imaging apparatus that includes a thermally conductive material disposed in a gap for radiating heat from the radiation detector to a rotating plate, and a heat dissipation mechanism having a drive unit that moves the thermally conductive material from a position where it is not in contact with the rotating plate or the radiation detector to a position where the thermally conductive material is in thermal conduction between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the program comprising: obtaining information about the heat output of the radiation detector; The computer executes a procedure for controlling the driving of the heat conductive material by the driving unit based on the information about the heat generation amount. [Effects of the Invention]

[0017] According to the present disclosure, when setting an imaging range, feature points can be detected appropriately according to the condition of the subject. [Brief explanation of the drawings]

[0018] [Figure 1] FIG. 1 is a diagram illustrating a schematic configuration of a CT apparatus, which is an example of a radiation imaging apparatus according to a first embodiment of the present disclosure. [Figure 2] FIG. 1 is a perspective view schematically illustrating a configuration of a detector; [Figure 3] FIG. 1 is an enlarged view of a portion where a detector is attached to a rotating plate in the CT apparatus according to the first embodiment; [Figure 4] Cross-sectional view of line II in Figure 3 (initial position of second member) [Figure 5] Cross-sectional view of line II in Figure 3 (second member operating position) [Figure 6] FIG. 10 is a diagram for explaining the configuration of a heat dissipation mechanism in a CT apparatus according to a second embodiment. [Figure 7] Cross-sectional view of line II-II in Figure 6 (initial position of second member) [Figure 8] Cross-sectional view of line II-II in Figure 6 (second member operating position) [Figure 9] 10 is a flowchart showing the processing performed in the second embodiment. [Figure 10] 10 is a flowchart showing the processing performed in the third embodiment. [Figure 11] FIG. 10 is a diagram for explaining the configuration of a heat dissipation mechanism in a CT scanner according to a fourth embodiment. [Figure 12] FIG. 10 is a diagram for explaining the operation of the heat dissipation mechanism in the fourth embodiment. [Figure 13] FIG. 10 is a diagram for explaining the operation of the heat dissipation mechanism in the fourth embodiment. [Figure 14] FIG. 10 is a diagram for explaining the operation of the heat dissipation mechanism in the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0019] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. A CT device according to a first embodiment is a PCCT device that detects radiation emitted from a radiation source and generates a radiographic image based on an electrical signal corresponding to the number of photons of the radiation. In this embodiment, a case where the radiation is X-rays will be described as an example.

[0020] 1 is a diagram schematically showing the configuration of a CT apparatus, which is an example of a radiation imaging apparatus according to the first embodiment. The CT apparatus 2 includes an X-ray source 3, an X-ray detector 4, a gantry 5, a bed 6, a control unit 7, and an image processing unit 8. A circular opening 51 is provided in the center of the gantry 5 for placing the bed 6 on which the subject H is placed. The gantry 5 also includes a rotating plate 52 fixed in a position where the X-ray source 3 and the X-ray detector 4 (hereinafter simply referred to as the detector 4) face each other, and a drive mechanism (not shown) for rotating the rotating plate 52. In the first embodiment, a heat dissipation mechanism 57 is provided between the rotating plate 52 and the detector 4.

[0021] Hereinafter, in this disclosure, the circumferential direction of the opening 51 is referred to as the X direction, the radial direction as the Y direction, and the central axis direction as the Z direction (see FIG. 2). The Z direction is perpendicular to the X and Y directions and generally corresponds to the body axis direction of the subject H.

[0022] The X-ray source 3 includes an X-ray tube 31, an X-ray filter 32, and a bowtie filter 33. The X-ray tube 31 generates X-rays and irradiates the object H with the generated X-rays. The X-ray filter 32 adjusts the dose of X-rays irradiated from the X-ray tube 31. In order to suppress the dose of radiation in the peripheral area, the bowtie filter 33 increases the dose near the center and decreases the dose in the periphery, thereby optimizing the dose of radiation.

[0023] 2, the X-ray detector 4 is configured by arranging a plurality of detector modules 40 in an arc shape in the X direction. Each of the detector modules 40 includes a collimator 41, a semiconductor layer 42, and an ASIC (Application Specific Integrated Circuit) 43. In addition, a plurality of heaters 46 (four in FIG. 1) and a plurality of cooling fans 47 (three in FIG. 1) are attached to the housing of the X-ray detector 4.

[0024] The collimator 41 is disposed on the X-ray incident side of the semiconductor layer 42, and removes scattered rays by restricting the direction of incidence of X-rays on the semiconductor layer 42. The semiconductor layer 42 is formed of cadmium zinc telluride (CZT), cadmium telluride (CdTe), or the like, and converts the incident X-rays that have passed through the subject H into charges equivalent to photons and outputs them.

[0025] The ASIC 43 is disposed on the opposite side of the semiconductor layer 42 from the collimator 41. The ASIC 43 is a circuit element having a photon counting circuit 44. The photon counting circuit 44 counts the number of charges output by the semiconductor layer 42 as the number of photons and outputs a counting signal. Electrodes for applying a high voltage to the semiconductor layer 42 are formed on the upper and lower surfaces of the semiconductor layer 42. By patterning the electrodes on the lower surface side of the semiconductor layer 42, multiple pixels are formed in the semiconductor layer 42. The photon counting circuit 44 counts photons for each pixel and outputs a counting signal.

[0026] A temperature sensor 45 is provided inside the ASIC 43 to measure the temperature of the ASIC 43 and output the measurement value. The temperature of the ASIC 43 changes in accordance with the temperature change of the semiconductor layer 42 caused by the current flow caused by the incidence of photons on the semiconductor layer 42. The temperature change of the ASIC 43 when X-rays are incident on it depends on the photon counting rate of the photon counting circuit 44.

[0027] The heater 46 is driven and controlled by the control unit 7 to heat the plurality of detector modules 40 of the detector 4 and increase the temperature of the ASIC 43 .

[0028] The cooling fans 47 are arranged to blow air from the Z direction onto the plurality of detector modules 40. The plurality of cooling fans 47 are controlled and driven by the control unit 7. As a result, the cooling fans 47 cool the ASIC 43, thereby lowering the temperature of the ASIC 43.

[0029] The control unit 7 is composed of a processor such as a CPU (Central Processing Unit). The control unit 7 controls the operations of the X-ray source 3, the X-ray detector 4, the gantry 5, and the bed 6. Specifically, the control unit 7 controls the emission of X-rays from the X-ray tube 31 of the X-ray source 3, the detection of X-rays by the X-ray detector 4, the rotation of the rotating plate 52 of the gantry 5, and the movement of the bed 6. The control unit 7 also acquires a count signal output from the photon counting circuit 44 of the ASIC 43 and a temperature measurement value output from the temperature sensor 45.

[0030] The control unit 7 is equipped with an auto exposure control (AEC). The control unit 7 uses the AEC to automatically determine the tube current for the X-ray tube 31 based on, for example, a positioning image for positioning before imaging. The control unit 7 then controls the drive of the X-ray tube 31 so that X-rays are emitted at the determined tube voltage.

[0031] Furthermore, when it is necessary to increase the temperature of the detector module 40 based on the temperature measurement value from the temperature sensor 45, the control unit 7 drives the heater 46 to increase the temperature of the detector module 40. On the other hand, when it is necessary to decrease the temperature of the detector module 40, the control unit 7 drives the cooling fan 47 to cool the detector module 40.

[0032] The supply of power, the supply of control signals, and the extraction of data between the control unit 7 and the X-ray source 3 and X-ray detector 4 are carried out via slip rings (not shown) provided between the X-ray source 3 and X-ray detector 4 and the rotating plate 52.

[0033] The image processing unit 8 is an image processing processor that generates a tomographic image (i.e., a CT image) by performing reconstruction processing based on the count signals acquired by the control unit 7 from each ASIC 43. The image processing unit 8 may be configured as a part of the control unit 7.

[0034] In addition, the control unit 7 is connected to an input device 9, a display device 10, a storage device 11, and a communication device 12. The input device 9 is a device for an operator to input operation instructions and is composed of a keyboard, a mouse, etc. The display device 10 is a display such as a liquid crystal display, and displays an operation screen, tomographic images, etc. The storage device 11 is a memory, a storage device, etc., and stores tomographic images, programs, various information, etc.

[0035] The communication device 12 is a communication interface for communicating with a radiology information system (RIS), a picture archiving and communication system (PACS), etc. The communication device 12 controls transmission in accordance with communication protocols defined by various wired or wireless communication standards.

[0036] Fig. 3 is an enlarged view of the attachment portion of the detector 4 to the rotating plate 52 in the CT apparatus according to the first embodiment. The cooling fan 47 of the detector 4 is omitted in Fig. 3. As shown in Fig. 3, the detector 4 is provided with three cylindrical legs 48 spaced apart from each other, and the detector 4 is attached to the rotating plate 52 by the three legs 48 with a gap between them. An insulating and heat-insulating material such as glass epoxy is interposed between the legs 48 and the rotating plate 52.

[0037] A heat dissipation mechanism 57 according to the first embodiment is provided in the gap between the detector 4 and the rotating plate 52, which dissipates heat from the detector 4 to the rotating plate 52. The heat dissipation mechanism 57 in the first embodiment has a thermally conductive material 60 and a spring 63. When the temperature of the detector 4 rises, the thermally conductive material 60 is moved from a position where it is not in contact with the rotating plate 52 or the detector 4 to a position where it conducts heat between the detector 4 and the rotating plate 52. For this reason, the thermally conductive material 60 is attached so that it can be inserted into and retracted from the gap between the detector 4 and the rotating plate 52.

[0038] FIG. 4 is a cross-sectional view taken along line II in FIG. 3. As shown in FIG. 4, the thermally conductive material 60 is made up of a first member 61 and a second member 62 each having a right-angled triangular prism shape. The first member 61 and the second member 62 are arranged to be able to slide against each other in the gap between the detector 4 and the rotating plate 52, with the long sides of the right-angled triangular prism shown in FIG. 4 acting as sliding surfaces 60A. The sliding surfaces 60A are inclined with respect to the surfaces on which the rotating plate 52 and the detector 4 face each other. The first member 61 and the second member 62 are made of a thermally conductive material. The sliding surfaces 60A between the first member 61 and the second member 62 are processed to have a surface roughness that allows the first member 61 and the second member 62 to slide against each other.

[0039] The thermally conductive material is preferably one that has a thermal conductivity of 200 (W / m K) or more, and more preferably a thermal conductivity of more than 400 (W / m K), when the thermal conductivity is measured in air at room temperature (25°C) using a disk with a diameter of 10 mm and a thickness of 1 mm as a sample by the laser flash method based on JIS R 1611: 2010. Examples of such materials include aluminum and copper.

[0040] The surface of the first member 61 opposite to the sliding surface 60A is fixed to the rotary plate 52. A spring 63 is arranged along the radial direction of the rotary plate 52. A support portion 53 protrudes toward the detector 4 on the radially inner side of the rotary plate 52, and one end of the spring 63 is fixed to the support portion 53. The other end of the spring 63, which is located on the radially outer side of the rotary plate 52, is fixed to the surface of the second member 62 on the radially inner side of the rotary plate 52. When the rotary plate 52 is not rotating, the second member 62 is located in an initial position away from the detector 4 as shown in FIG. 4.

[0041] When imaging the subject H in the CT device 2, the rotating plate 52 rotates at a predetermined angular velocity. When the rotating plate 52 rotates, a centrifugal force acts on the second member 62, and the second member 62 moves outward from the center of rotation of the rotating plate 52 against the spring force of the spring 63. As a result, as shown in Fig. 5, the second member 62 maintains contact with the first member 61, while the surface opposite the sliding surface 60A comes into contact with the detector 4. The position of the second member 62 shown in Fig. 5 is the operating position.

[0042] The spring constant of the spring 63 is determined based on the angular velocity at which the rotating plate 52 rotates, the position of the second member 62 in the radial direction of the rotating plate 52, and the weight of the second member 62, so that the second member 62 is located in the initial position shown in Fig. 4 when the rotating plate 52 is not rotating, and moves to the operating position shown in Fig. 5 when the rotating plate 52 rotates. The position of the second member 62 in the radial direction of the rotating plate 52 is, for example, the position of the center of gravity of the second member 62 in the radial direction of the rotating plate 52.

[0043] When imaging the subject H, X-ray photons incident on the semiconductor layer 42 of the detector module 40 are converted into electric charges, and the photon counting circuit 44 counts the converted electric charges. This causes the detector module 40 to generate heat. At this time, the temperature sensor 45 measures the temperature of the detector module 40, and if the heat generation is insufficient, the heater 46 is driven to heat the detector module 40. On the other hand, if the heat generation is large and the temperature measured by the temperature sensor 45 exceeds a predetermined threshold value Th0, the cooling fan 47 is driven to cool the detector module 40.

[0044] However, there are cases where the photon counting circuit 44 generates too much heat and cooling by the cooling fan 47 alone is insufficient. Such insufficient cooling occurs when imaging the subject H. During imaging, the rotating plate 52 rotates. In the first embodiment, when the rotating plate 52 rotates, centrifugal force acts on the second member 62 of the thermally conductive material 60, and the second member 62 moves from the initial position shown in FIG. 4 to the operating position shown in FIG. 5 against the spring force of the spring 63. At the operating position, the detector 4 comes into contact with the rotating plate 52 via the thermally conductive material 60. Because the rotating plate 52 is made of metal and the thermally conductive material 60 is made of a thermally conductive material, heat from the detector 4 is released to the rotating plate 52 via the thermally conductive material 60.

[0045] In this way, in the first embodiment, in a situation where the detector 4 generates more heat, the detector 4 can be cooled more significantly by the heat dissipation mechanism 57, and therefore the temperature of the detector 4 can be kept constant.

[0046] Next, a second embodiment of the present disclosure will be described. In the second embodiment, the same components as those in the first embodiment are assigned the same reference numerals, and detailed description thereof will be omitted. FIG. 6 is a diagram illustrating the configuration of a heat dissipation mechanism in a CT scanner 2 according to the second embodiment, and FIGS. 7 and 8 are cross-sectional views taken along line II-II in FIG. 6. As shown in FIG. 6, a heat dissipation mechanism 57A according to the second embodiment is provided in the gap between the detector 4 and the rotating plate 52, dissipating heat from the detector 4 to the rotating plate 52. The heat dissipation mechanism 57A in the second embodiment includes a thermally conductive material 60 made up of a first member 61 and a second member 62, similar to the heat dissipation mechanism 57 in the first embodiment.

[0047] In the first embodiment, the second member 62 is moved against the spring 63 by centrifugal force generated by the rotation of the rotating plate 52. In the second embodiment, the heat dissipation mechanism 57A has a motor 64 and a ball screw 65 that is threadedly engaged with the second member 62, and the ball screw 65 is rotated by the motor 64 to move the second member 62 from the initial position in Fig. 7 to the operating position shown in Fig. 8. The motor 64 and the ball screw 65 are an example of a drive unit of the present disclosure.

[0048] A support portion 54 protrudes radially inward from the rotating plate 52 toward the detector 4, and a motor 64 is attached to the support portion 54. One end of a ball screw 65 is attached to the rotating shaft of the motor 64, and the other end is threadedly engaged with a threaded hole 62A formed in the second member 62. When the motor 64 is rotated in a predetermined direction with the second member 62 in the initial position as shown in FIG. 7, the second member 62 moves to the operating position as shown in FIG. 8. In the operating position, the second member 62 maintains contact with the first member 61 while the surface opposite the sliding surface 60A comes into contact with the detector 4. In this state, heat from the detector 4 is dissipated to the rotating plate 52 via the thermally conductive material 60. On the other hand, when the motor 64 is rotated in a direction opposite to the predetermined direction with the second member 62 in the operating position as shown in FIG. 8, the second member 62 moves to the initial position as shown in FIG. 7.

[0049] In the second embodiment, the motor 64 is rotated by a control signal from the control unit 7 based on the measurement result of the temperature sensor 45. Fig. 9 is a flowchart showing the processing performed by the control unit 7 in the second embodiment. Note that in the second embodiment, the control unit 7 drives the heater 46 and the cooling fan 47 to maintain the temperature of the detector module 40 at a constant temperature, but a description of the driving of the heater 46 and the cooling fan 47 will be omitted here.

[0050] 9, the control unit 7 monitors whether the temperature of the detector module 40 measured by the temperature sensor 45 is equal to or higher than a predetermined threshold value Th1 (step ST1). The threshold value Th1 is, for example, a temperature at which the detector module 40 cannot be kept constant even when the cooling fan 47 is driven, and is a temperature higher than the threshold value Th0 described above. If the result of step ST1 is affirmative, the control unit 7 drives the motor 64 to rotate in a predetermined direction (step ST2). This moves the second member 62 from the initial position to the operating position, and the temperature of the detector 4 is dissipated to the rotating plate 52 via the thermally conductive material 60.

[0051] Next, the control unit 7 starts monitoring whether the temperature measured by the temperature sensor 45 is below the threshold value Th1 (step ST3). If the result of step ST3 is affirmative, the control unit 7 drives the motor 64 to rotate in the direction opposite to the predetermined direction (step ST4) and returns to step ST1. This moves the second member 62 from the operating position to the initial position. In this state, temperature control is performed by the heater 46 and the cooling fan 47.

[0052] As described above, in the second embodiment, when the temperature of the detector module 40 becomes equal to or higher than the threshold value Th1, the motor 64 is driven in a predetermined direction to move the second member 62 from the initial position to the operating position. In the operating position, the detector 4 comes into contact with the rotating plate 52 via the thermally conductive material 60. Because the rotating plate 52 is made of metal and the thermally conductive material 60 is made of a thermally conductive material, heat from the detector 4 is dissipated to the rotating plate 52 via the thermally conductive material 60. Therefore, in the second embodiment, in a situation where the detector 4 generates more heat, the detector 4 can be cooled more significantly by the heat dissipation mechanism 57, thereby maintaining a constant temperature of the detector 4.

[0053] In the second embodiment, the motor 64 is driven based on the temperature detected by the temperature sensor 45 to move the second member 62 from the initial position to the operating position, but this is not limited to this. The driving of the motor 64 may also be controlled based on the X-ray irradiation conditions during imaging. This will be described below as a third embodiment. In the third embodiment, only the processing performed by the control unit 7 differs from the second embodiment, and the configuration of the heat dissipation mechanism 57A is the same as that of the second embodiment, so a detailed description of the configuration will be omitted.

[0054] 10 is a flowchart showing the processing performed in the third embodiment. It is assumed that the second member 62 is in the initial position. As described above, the heat generated by the photon counting circuit 44 is proportional to the number of X-ray photons counted, so the larger the tube current value of the X-ray exposure, the greater the amount of heat generated by the photon counting circuit 44. In this embodiment, the control unit 7 is equipped with an AEC, and automatically sets the tube current when driving the X-ray source 3 (step ST11).

[0055] In the third embodiment, the control unit 7 determines whether the temperature of the photon counting circuit 44 becomes equal to or higher than a predetermined threshold value Th1 when the subject H is imaged using the set tube current (step ST12). If the result of step ST12 is affirmative, the control unit 7 drives the motor 64 in a predetermined direction (step ST13) to move the second member 62 from the initial position to the operating position, and ends the process for driving the heat dissipation mechanism 57A. If the result of step ST12 is negative, the control unit 7 ends the process for driving the heat dissipation mechanism 57A.

[0056] As described above, in the third embodiment, when a tube current is set such that the temperature of the detector module 40 becomes equal to or higher than the threshold value Th1, the motor 64 is driven in a predetermined direction to move the second member 62 from the initial position to the operating position. At the operating position, the detector 4 comes into contact with the rotating plate 52 via the thermally conductive material 60. Because the rotating plate 52 is made of metal and the thermally conductive material 60 is made of a thermally conductive material, heat from the detector 4 is dissipated to the rotating plate 52 via the thermally conductive material 60. Therefore, in the second embodiment, in a situation where the detector 4 generates more heat, the detector 4 can be cooled more significantly by the heat dissipation mechanism 57A, thereby maintaining a constant temperature of the detector 4.

[0057] Next, a fourth embodiment of the present disclosure will be described. In the fourth embodiment, the same components as those in the first embodiment are given the same reference numerals, and detailed description thereof will be omitted here. Fig. 11 is a diagram for explaining the configuration of a heat dissipation mechanism in a CT device 2 according to the fourth embodiment. As shown in Fig. 11, the fourth embodiment differs from the first embodiment in that a plurality of heat dissipation mechanisms 57B are provided, each driven by a motor 64 and a ball screw 65, as in the second embodiment.

[0058] In the fourth embodiment, the heat-conducting material included in the heat dissipation mechanism 57B is divided into a plurality of small members 70 radially relative to the rotation axis of the rotating plate 52. As in the first to third embodiments, the small members 70 are made up of a first member 61 and a second member 62, and the second member 62 of each of the small members 70 is moved between an initial position and an operating position by a motor 64 and a ball screw 65. In the fourth embodiment, the control unit 7 moves the second members 62 of the plurality of small members 70 individually to their operating positions, thereby making it possible to change the heat dissipation position and amount from the detector 4 to the rotating plate 52.

[0059] 2, the detector 4 has a plurality of detector modules 40 arranged in an arc shape in the X direction. Meanwhile, during imaging, the X-ray irradiation dose to the detector modules 40 varies depending on the physique or imaging region of the subject H. When the X-ray irradiation dose varies, a detector module 40 with a relatively large X-ray irradiation dose generates more heat than a detector module 40 with a relatively small X-ray irradiation dose.

[0060] In the fourth embodiment, for example, when the temperature of the detector module 40 near the center of the detector 4 exceeds the threshold value Th1, or when the imaging conditions are such that a temperature rise in the detector module 40 near the center of the detector 4 is expected, the second member 62 of the small member 70 near the center of the detector 4 is moved from the initial position to the operating position as shown in FIG. 12. Furthermore, when the imaging region of the subject H has a narrow X-ray irradiation range, such as the head or extremities, the temperature of the detector module 40 near the ends of the detector 4 rises or is expected to rise. In such a case, as shown in FIG. 13, the second member 62 of the small member 70 near both ends of the detector 4 is moved from the initial position to the operating position. Furthermore, when the temperature of the detector module 40 over the entire detector 4 exceeds the threshold value Th1, or when the imaging conditions are such that a temperature rise in the detector module 40 over the entire detector 4 is expected, the second member 62 of all the heat dissipation mechanisms 57B is moved from the initial position to the operating position as shown in FIG. 14.

[0061] As a result, in the fourth embodiment, it is possible to largely cool only the detector module 40 which generates a larger amount of heat in the detector 4. Therefore, it is possible to more efficiently maintain the temperature of the detector 4 at a constant temperature.

[0062] In the above-described embodiments, the first member 61 is fixed to the rotating plate 52, but the present invention is not limited to this. The first member 61 may be fixed to the detector 4, and the second member 62 may be moved from the initial position to the operating position, thereby bringing the second member 62 into contact with the rotating plate 52 and dissipating heat from the detector 4 to the rotating plate 52.

[0063] In each of the above embodiments, the temperature sensor 45 is provided inside each ASIC 43, but the temperature sensor 45 may be provided outside the ASIC 43. For example, multiple temperature sensors 45 may be arranged in a housing that houses the detector 4. The multiple temperature sensors 45 are preferably arranged evenly in the X and Z directions. In this case, the control unit 7 may acquire the measured temperature value T of each ASIC 43 from the temperature sensor 45 arranged near each ASIC 43.

[0064] In addition, in each of the above embodiments, the temperature sensor 45 is used to measure the temperature of the detector module 40, but this is not limiting. It may also be a device that can measure the temperature of the entire X-ray detector 4, such as a thermography camera.

[0065] Furthermore, in the second to fourth embodiments, the second member 62 is moved by the motor 64 and the ball screw 65, but this is not limiting. A feed screw may be used instead of the ball screw 65. Alternatively, the motor 64 and the second member 62 may both be provided with meshing screws, and the rotation of the screw provided in the motor 64 may rotate the screw of the second member 62, thereby moving the second member 62.

[0066] Furthermore, in the above embodiments, X-rays are used as radiation, but gamma rays may also be used as radiation.

[0067] In the above embodiment, the hardware structure of the control unit 7 can be implemented using various processors as shown below.

[0068] In addition to CPUs, which are general-purpose processors that execute programs and function as various processing units, these include PLDs (Programmable Logic Devices) such as FPGAs (Field-Programmable Gate Arrays), whose circuit configuration can be changed after manufacturing, and dedicated electrical circuits such as ASICs, which are processors with circuit configurations designed specifically to execute specific processes.

[0069] The above-mentioned various processes may be executed by one of these various processors, or may be executed by a combination of two or more processors of the same or different types (for example, a plurality of FPGAs, or a combination of a CPU and an FPGA). Also, a plurality of processing units may be configured by a single processor. An example of configuring a plurality of processing units by a single processor is a form in which a processor is used that realizes the functions of an entire system including a plurality of processing units by a single IC (Integrated Circuit) chip, such as an SoC (System on a Chip).

[0070] The following are appendices to the present disclosure.

[0071] (Additional note 1) a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a thermally conductive material disposed in the gap for dissipating heat from the radiation detector to the rotating plate, A radiation imaging device in which, when the temperature of the radiation detector rises, the thermally conductive material is moved from a non-contact position with the rotating plate or the radiation detector to a position that thermally conducts between the radiation detector and the rotating plate. (Additional note 2) the thermally conductive material includes a first member and a second member having sliding surfaces inclined with respect to the surfaces of the rotating plate and the radiation detector that face each other; The radiation imaging device according to appended claim 1, wherein the first member is fixed to the rotating plate or the radiation detector in the gap, the second member is located at a position away from the rotating plate or the radiation detector in an initial position, and the second member slides relative to the first member and is moved to an operating position in which the second member contacts the radiation detector or the rotating plate while maintaining contact with the first member when the temperature of the radiation detector rises. (Additional note 3) the heat dissipation mechanism includes a spring arranged along a radial direction of the rotary plate, the spring having one end fixed to the rotary plate or the radiation detector and the other end located radially outward of the rotary plate relative to the one end fixed to the second member; The radiation imaging device described in Appendix 2, wherein the spring constant of the spring is determined based on the angular velocity at which the rotating plate rotates, the radial position of the second member relative to the rotating plate, and the weight of the second member. (Additional note 4) the heat dissipation mechanism includes a drive unit having a motor and a ball screw whose one end is fixed to the motor and whose other end is screwed into the second member, The radiation imaging device described in Appendix 2, wherein the drive unit drives the motor based on information regarding the heat generation amount of the radiation detector, thereby moving the second member from the initial position to the operating position and from the operating position to the initial position. (Additional note 5) 5. The radiation imaging apparatus according to claim 4, wherein the information relating to the amount of heat generated is a temperature measured by a temperature sensor provided in the radiation detector. (Additional note 6) 5. The radiation imaging apparatus according to claim 4, wherein the information regarding the amount of heat generated is information based on a tube current applied to the radiation source. (Additional note 7) the thermally conductive material is divided into a plurality of small members radially with respect to the rotation axis, 7. The radiation imaging device according to any one of appendix items 4 to 6, wherein the drive unit changes the positions and the number of the small members that provide thermal conduction between the radiation detector and the rotating plate, depending on at least one of the position at which the temperature of the radiation detector rises and the amount of heat generated. (Additional note 8) a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the method comprising: a computer acquires information regarding the amount of heat generated by the radiation detector; A temperature control method for controlling the driving of the thermally conductive material by the driving unit based on information about the amount of heat generated. (Additional note 9) a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the temperature control program causing a computer to execute a temperature control method for a radiation imaging apparatus including: a heat conductive material disposed in the gap for dissipating heat from the radiation detector to the rotating plate; and a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the temperature control program comprising: acquiring information about the amount of heat generated by the radiation detector; and a temperature control program that causes a computer to execute a procedure for controlling the driving of the thermally conductive material by the driving unit based on information about the amount of heat generated. [Explanation of symbols]

[0072] 2. Radiography equipment 3 X-ray source 4 X-ray detector 5 Gantry 6 berths 7 Control Unit 8 Image processing section 9 Input Devices 10 Display device 11 Storage device 12. Communications equipment 31 X-ray tube 32 X-ray filters 33 Bowtie Filter 40 detector modules 41 Collimator 42 Semiconductor layer 43 ASIC 44 Photon counting circuit 45 Temperature Sensor 46 Heater 47 Cooling fan 48 Legs 50 Thermal Conductive Materials 51 Opening 52 Rotating Plate 53,54 Support part 57,57A,57B Heat dissipation mechanism 60 Thermal Conductive Materials 60A sliding surface 61 First member 62 Second member 62A screw hole 64 motor 65 Ball screw 70 Small parts H Subject

Claims

1. a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a thermally conductive material disposed in the gap for dissipating heat from the radiation detector to the rotating plate, A radiation imaging device in which, when the temperature of the radiation detector rises, the thermally conductive material is moved from a non-contact position with the rotating plate or the radiation detector to a position that thermally conducts between the radiation detector and the rotating plate.

2. the thermally conductive material includes a first member and a second member having sliding surfaces inclined with respect to the surfaces of the rotating plate and the radiation detector that face each other; 2. The radiation imaging device according to claim 1, wherein the first member is fixed to the rotating plate or the radiation detector in the gap, the second member is located at a position away from the rotating plate or the radiation detector in an initial position, and the second member slides relative to the first member and is moved to an operating position in which the second member contacts the radiation detector or the rotating plate while maintaining contact with the first member when the temperature of the radiation detector rises.

3. the heat dissipation mechanism includes a spring arranged along a radial direction of the rotary plate, the spring having one end fixed to the rotary plate or the radiation detector and the other end located radially outward of the rotary plate relative to the one end fixed to the second member, 3. The radiographic imaging apparatus according to claim 2, wherein the spring constant of the spring is determined based on an angular velocity at which the rotary plate rotates, a position of the second member in a radial direction of the rotary plate, and a weight of the second member.

4. the heat dissipation mechanism includes a drive unit having a motor and a ball screw having one end fixed to the motor and the other end screwed into the second member, 3. The radiation imaging apparatus according to claim 2, wherein the drive unit drives the motor based on information about the amount of heat generated by the radiation detector, thereby moving the second member from the initial position to the operating position and from the operating position to the initial position.

5. 5. The radiographic imaging apparatus according to claim 4, wherein the information relating to the amount of heat generated is a temperature measured by a temperature sensor provided in the radiation detector.

6. The radiographic imaging apparatus according to claim 4 , wherein the information relating to the amount of heat generated is information based on a tube current applied to the radiation source.

7. the thermally conductive material is divided into a plurality of small members radially with respect to the rotation axis, 7. The radiographic imaging apparatus according to claim 4, wherein the drive unit changes the positions and the number of the small members that provide thermal conduction between the radiation detector and the rotating plate, depending on at least one of a position in the radiation detector where the temperature rises and the amount of heat generated.

8. a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the method comprising: a computer acquires information regarding the amount of heat generated by the radiation detector; A temperature control method for controlling the driving of the thermally conductive material by the driving unit based on information about the amount of heat generated.

9. a thermally conductive rotating plate to which the radiation source is fixed and which rotates around a rotation axis; a radiation detector including a thermally conductive housing, the radiation detector being fixed to the rotating plate at a position facing the radiation source across the rotation axis with a partial gap between the rotating plate and the radiation detector; a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the temperature control program causing a computer to execute a temperature control method for a radiation imaging apparatus including: a heat conductive material disposed in the gap for dissipating heat from the radiation detector to the rotating plate; and a heat dissipation mechanism having a drive unit that moves the heat conductive material from a non-contact position with the rotating plate or the radiation detector to a position where the heat conductive material is thermally conductive between the radiation detector and the rotating plate when the temperature of the radiation detector rises, the temperature control program comprising: acquiring information about the amount of heat generated by the radiation detector; and a temperature control program that causes a computer to execute a procedure for controlling the driving of the thermally conductive material by the driving unit based on information about the amount of heat generated.

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