Radiographic apparatus and method for controlling radiographic apparatus

Abstract

The invention provides a radiographic apparatus and a method for controlling the radiographic apparatus, wherein the temperature difference of a plurality of circuit elements including a photon counting circuit can be suppressed. The radiographic imaging device detects radiation emitted from a radiation source and generates a radiographic image on the basis of an electric signal corresponding to the number of photons of the radiation, and is provided with: a plurality of circuit elements having a photon counting circuit that counts photons; a temperature measuring device that measures the temperature of a region in which the plurality of circuit elements are disposed; and a processor that adjusts the temperature of the plurality of circuit elements by performing drive control of the plurality of circuit elements on the basis of a measured value of the temperature measured by the temperature measurement device during a standby period, which is a period during which the photon counting circuit does not count the photons.

Description

Technical Field

[0001] The technology of the present invention relates to a radiographic apparatus and a control method of the radiographic apparatus. Background Art

[0002] In recent years, radiographic imaging devices equipped with photon-counting detectors, known as PCCT (Photon Counting Computed Tomography) devices, have become known. Unlike the charge-integrating detectors used in conventional CT (Computed Tomography) devices, photon-counting detectors count incident radiation photons. PCCT devices can measure the energy of each photon, thus providing more information than conventional CT devices.

[0003] In a PCCT device, incident photons are converted into electric charges in a semiconductor layer, and the converted charges are counted by a photon counting circuit. It is known that such photon counting detectors generate heat as they count photons, and the amount of heat generated varies depending on the count rate (for example, see Patent Document 1).

[0004] Since the characteristics of a photon counting circuit change due to temperature changes, Patent Document 1 proposes suppressing the temperature changes by providing a heat generation compensation circuit that controls the amount of heat generated by the photon counting circuit according to the counting rate.

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2018-143575

[0006] However, the technology described in Patent Document 1 does not account for standby periods during which no image capture is taking place and the photon counting circuit is not counting photons. A photon-counting detector comprises multiple circuit elements including photon counting circuits. The count rate during image capture varies for each photon counting circuit, and therefore the temperature at the end of image capture varies for each circuit element. For example, circuit elements located in areas of the subject with low radiation absorption and high radiation transmission will experience a higher count rate from the photon counting circuit.

[0007] Therefore, during standby, the temperature of each circuit component may vary significantly. If imaging is performed in a state where the temperature of each circuit component varies significantly, the technique described in Patent Document 1, which controls the amount of heat generated based on the count rate, cannot suppress the temperature differences between each circuit component. The temperature differences between each circuit component result in differences in dark current noise, etc., causing degradation such as unevenness in the tomographic image. Summary of the Invention

[0008] Therefore, the technology according to the present invention provides a radiographic apparatus and a method for controlling the radiographic apparatus that can suppress temperature differences among a plurality of circuit elements including a photon counting circuit.

[0009] The technology involved in the present invention is a radiographic apparatus that detects radiation emitted from a radiation source and generates a radiographic image based on an electrical signal corresponding to the number of photons in the radiation, and includes: a plurality of circuit elements having a photon counting circuit that counts photons; a temperature measuring device that measures the temperature of an area where the plurality of circuit elements are arranged; and a processor that adjusts the temperature of the plurality of circuit elements by controlling the drive of the plurality of circuit elements based on the temperature measured by the temperature measuring device during a period in which the photon counting circuit is not counting photons, that is, a standby period.

[0010] Preferably, the temperature measuring device is composed of a plurality of temperature sensors.

[0011] Preferably, each of the plurality of temperature sensors is provided inside each of the plurality of circuit elements.

[0012] Preferably, the processor performs the following processing: storing the measured values ​​of the temperatures of the plurality of circuit elements measured by the temperature measuring device during calibration as target values; and performing drive control during the standby period so that the measured values ​​approach the target values.

[0013] It is also preferable that the processor performs the following processing: predicting temperature changes of the plurality of circuit elements during the standby period; and performing drive control based on the predicted temperature changes.

[0014] Preferably, the processor performs the following processing: acquiring imaging plan information; and determining, based on the acquired imaging plan information, a period from the completion of one imaging operation to the execution of the next imaging operation as the standby period.

[0015] Preferably, the processor performs a process for performing drive control so that the temperature of each of the plurality of circuit elements reaches a target value when the standby period ends.

[0016] The preferred processor performs the following processing: for each of the multiple circuit elements, an estimated temperature is calculated that is estimated to be reached when the standby period ends without drive control; when any of the multiple estimated temperatures is higher than the target value, the highest temperature among the multiple estimated temperatures is used as the target value for drive control.

[0017] Preferably, at least one cooling fan is provided for cooling the plurality of circuit elements.

[0018] Preferably, the processor performs processing for driving at least one cooling fan when any one of the plurality of measurement values ​​measured by the temperature measurement device is higher than a target value.

[0019] Preferably, the processor performs processing for controlling the rotation of at least one cooling fan so that the temperatures of the plurality of circuit elements approach target values ​​when the standby period ends.

[0020] In the control method of a radiographic apparatus involved in the technology of the present invention, the radiographic apparatus is a radiographic apparatus 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, and the radiographic apparatus includes: a plurality of circuit elements having a photon counting circuit that counts photons; a temperature measuring device that measures the temperature of an area where the plurality of circuit elements are arranged; and a processor, wherein the processor executes a process including the following steps: during a period in which the photon counting circuit does not count photons, i.e., a standby period, the temperature of the plurality of circuit elements is adjusted by driving and controlling the plurality of circuit elements based on a temperature measurement value measured by the temperature measuring device.

[0021] Effects of the Invention

[0022] According to the technology of the present invention, it is possible to provide a radiographic apparatus and a method for controlling the radiographic apparatus that can suppress temperature differences among a plurality of circuit elements including a photon counting circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a diagram schematically showing the configuration of a radiographic apparatus according to the first embodiment.

[0024] Figure 2 It is a perspective view schematically showing the structure of an X-ray detector.

[0025] Figure 3 This is a diagram schematically showing a configuration example of a detector module.

[0026] Figure 4 This is a diagram showing the flow of drive control performed by the control unit according to the first embodiment.

[0027] Figure 5 This is a graph showing the relationship between the measured temperature value and the driving force.

[0028] Figure 6 This is a diagram showing an example of a calibration flow.

[0029] Figure 7 This is a diagram showing the flow of drive control performed by the control unit according to the second modification.

[0030] Figure 8 This is a diagram schematically showing an example of drive control according to the second modification example for one ASIC.

[0031] Figure 9 This is a diagram for explaining the subject of the second modification.

[0032] Figure 10 This is a diagram showing the flow of drive control performed by the control unit according to the third modification.

[0033] Figure 11 This is a diagram schematically showing the configuration of a radiographic apparatus according to the second embodiment.

[0034] Figure 12 This is a diagram showing a flow of drive control performed by a control unit according to the second embodiment.

[0035] Figure 13 This is a diagram showing another arrangement example of a plurality of temperature sensors.

[0036] Figure 14 This is a diagram showing the structure of a photon counting circuit.

[0037] Explanation of symbols

[0038] 2. 2a-Radiographic apparatus, 3-X-ray source, 4-X-ray detector, 4a-Container, 5-Frame, 6-Bed, 7-Control unit, 8-Image processing unit, 9-Input device, 10-Display device, 11-Storage device, 12-Communication device, 31-X-ray tube, 32-X-ray filter, 33-Butterfly filter, 40-Detector module, 41-Collimator, 42-Semiconductor layer, 42A-Upper electrode, 42B-Lower electrode, 43-ASIC, 44-Photon counting circuit, 44A-Amplifier circuit, 44B-Waveform shaping circuit, 44C-Comparator circuit, 44D-Counter circuit, 45-Temperature sensor, 46-Holding substrate, 50-Cooling fan, 51-Opening, 52-Rotating plate, H-Object. DETAILED DESCRIPTION

[0039] An embodiment of the technology of the present invention will be described below with reference to the accompanying drawings. The radiographic apparatus of the present invention is applicable to a PCCT apparatus that detects radiation emitted from a radiation source and generates a radiographic image based on an electrical signal corresponding to the number of photons in the radiation. In this embodiment, the case where the radiation is X-rays is used as an example.

[0040] [First embodiment]

[0041] Figure 1The structure of a radiographic apparatus 2 according to the first embodiment is schematically shown. The radiographic 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 arranging the bed 6 on which the subject H is placed. Furthermore, the gantry 5 is provided with a rotating plate 52 fixed at a position opposing the X-ray source 3 and the X-ray detector 4, and a drive mechanism (not shown) for rotating the rotating plate 52.

[0042] Hereinafter, in the present invention, the circumferential direction of the opening 51 is defined as the X direction, the radial direction is defined as the Y direction, and the central axis direction is defined as the Z direction (refer to FIG. Figure 2 ). The Z direction is orthogonal to the X direction and the Y direction, and is usually the body axis direction of the subject H.

[0043] The X-ray source 3 includes an X-ray tube 31, an X-ray filter 32, and a butterfly filter 33. The X-ray tube 31 generates X-rays and irradiates the generated X-rays to the subject H. The X-ray filter 32 adjusts the dose of X-rays irradiated from the X-ray tube 31. To suppress the radiation dose in the peripheral area, the butterfly filter 33 enhances the dose near the center and reduces the dose in the periphery to optimize the radiation dose.

[0044] like Figure 2 As shown, the X-ray detector 4 is configured by arranging a plurality of detector modules 40 in an arc shape in the X direction. Each detector module 40 includes a collimator 41 , a semiconductor layer 42 , and an ASIC (Application Specific Integrated Circuit) 43 .

[0045] The collimator 41 is located on the X-ray incident side of the semiconductor layer 42 and removes scattered radiation by limiting the direction of X-ray incidence on the semiconductor layer 42. The semiconductor layer 42 is formed of materials such as cadmium zinc telluride (CZT) and cadmium telluride (CdTe). It converts incident X-rays that have passed through the subject H into charges equivalent to photons and outputs them.

[0046] ASIC 43 is arranged on the side of semiconductor layer 42 opposite to collimator 41. ASIC 43 is a circuit element having a photon counting circuit 44. Photon counting circuit 44 counts the number of charges output by semiconductor layer 42 as the number of photons and outputs a count signal. Furthermore, electrodes for applying a high voltage to semiconductor layer 42 are formed on the upper and lower surfaces of semiconductor layer 42. By patterning the electrodes on the lower surface of semiconductor layer 42, a plurality of pixels are formed in semiconductor layer 42. Photon counting circuit 44 counts photons for each pixel and outputs a count signal. The count signal corresponds to the "electrical signal corresponding to the number of photons" involved in the technology of the present invention.

[0047] Furthermore, a temperature sensor 45 is provided within the ASIC 43 to measure the temperature of the ASIC 43 and output the measured value. The temperature of the ASIC 43 changes as the temperature of the semiconductor layer 42 changes due to the flow of current caused by the incidence of photons into the semiconductor layer 42. The temperature change of the ASIC 43 when X-rays are incident depends on the photon count rate of the photon counting circuit 44. The multiple temperature sensors 45 provided in the radiographic apparatus 2 are an example of a "temperature measuring device" according to the present invention.

[0048] The control unit 7 is composed of a processor such as a CPU (Central Processing Unit). It controls the operation of the X-ray source 3, X-ray detector 4, gantry 5, and bed 6. Specifically, the control unit 7 controls the X-ray irradiation from the X-ray tube 31 of the X-ray source 3, the X-ray detection by the X-ray detector 4, the rotation of the rotating plate 52 of the gantry 5, and the movement of the bed 6. Furthermore, the control unit 7 obtains the count signal output by the photon counting circuit 44 of the ASIC 43 and the temperature measurement value output by the temperature sensor 45.

[0049] The image processing unit 8 is an image processing processor that generates a tomographic image (also called a CT image) by performing reconstruction processing based on the count signals received from each ASIC 43 by the control unit 7. The image processing unit 8 can be configured as part of the control unit 7. A tomographic image is an example of a "radiological image" involved in the technology of the present invention.

[0050] Furthermore, an input device 9, a display device 10, a storage device 11, and a communication device 12 are connected to the control unit 7. The input device 9 is a device for the operator to input operational instructions and is composed of a keyboard, a mouse, etc. The display device 10 is a display such as a liquid crystal display, which displays operation screens, tomographic images, etc. The storage device 11 is a memory, a storage device, etc., which stores tomographic images, programs, various information, etc.

[0051] The communication device 12 is an interface for communication with radiology information systems (RIS), picture archiving and communication systems (PACS), etc. The communication device 12 performs transmission control according to communication protocols defined by various wired or wireless communication standards.

[0052] Furthermore, the ASIC 43 is configured to be able to change its temperature by being driven and controlled by the control unit 7 during the standby period when the photon counting circuit 44 is not counting photons. For example, the control unit 7 increases power consumption by idling the photon counting circuit 44, thereby raising the temperature of the ASIC 43. Specifically, the ASIC 43 is provided with a pseudo-pulse generation circuit that generates pseudo-pulses to cause the photon counting circuit 44 to perform pseudo-counting. The control unit 7 drives the pseudo-pulse generation circuit to generate heat in the ASIC 43. The control unit 7 can control the amount of heat generated by controlling the pulse generation rate generated by the pseudo-pulse generation circuit. The pulse generation rate refers to the number of pulses generated per unit time.

[0053] Alternatively, a self-heating heating circuit may be provided within ASIC 43 instead of the dummy pulse generating circuit. For example, the heating circuit includes a resistor. The control unit 7 controls the heating circuit to raise the temperature of ASIC 43. The control unit 7 can control the amount of heat generated by controlling the resistance of the heating circuit, the current flowing through the heating circuit, the on / off timing of the resistor, and other factors.

[0054] As described above, Japanese Patent Application Laid-Open No. 2018-143575 discloses a structure and a control method for changing the temperature of ASIC 43 .

[0055] Figure 3 The following schematically illustrates an example configuration of a detector module 40. For example, the detector module 40 includes four ASICs 43 mounted on a support substrate 46. The four ASICs 43 are arranged in the Z direction. A semiconductor layer 42 is connected to each ASIC 43. A collimator 41 is disposed on each of the four semiconductor layers 42. The number of ASICs 43 included in the detector module 40 is not limited to four and may be any appropriate number.

[0056] The photon count rate during imaging varies for each photon counting circuit 44 within the ASIC 43, resulting in a different temperature for each ASIC 43 at the end of imaging. For example, an ASIC 43 located in an area of ​​the subject H where the X-ray absorptivity is low and the amount of X-rays transmitted is high will have a higher count rate based on the photon counting circuit 44. Consequently, during the standby period of the radiographic apparatus 2, temperature differences arise among the multiple ASICs 43. During the standby period, photon counting is not performed, so while the temperature of each ASIC 43 decreases, the temperature differences between the individual ASICs 43 are not eliminated. This temperature difference can degrade the tomographic image.

[0057] To minimize temperature differences between the ASICs 43 during the standby period, the control unit 7 controls the drive of each ASIC 43 to adjust the temperature of each ASIC 43. The standby period is when the radiographic apparatus 2 is not performing imaging. As mentioned above, it is when the photon counting circuit 44 is not counting photons. For example, the standby period is the period from the end of one imaging session to the start of the next imaging session.

[0058] Figure 4 The following shows a flow of drive control by the control unit 7 according to the first embodiment. In this embodiment, the control unit 7 drives and controls each ASIC 43 so that the temperature of each ASIC 43 reaches a predetermined target value Ta during the standby period.

[0059] First, the control unit 7 determines whether it is in the standby period (step S10). If it is not in the standby period (step S10: No), the control unit 7 transfers the process to step S15. On the other hand, if it is in the standby period (step S10: Yes), the control unit 7 obtains the measured value T of the temperature of each ASIC 43 from each temperature sensor 45 (step S11).

[0060] The control unit 7 determines whether each measured value T is lower than the target value Ta (step S12). If all measured values ​​T are higher than the target value Ta (step S12: "No"), the control unit 7 transfers the process to step S15. On the other hand, if any measured value T is lower than the target value Ta (step S12: "Yes"), the control unit 7 determines the driving force for driving the ASIC 43 based on the temperature difference between the measured value T and the target value Ta (step S13). Figure 5 As shown, the lower the measured value T is than the target value Ta, the greater the driving force determined by the control unit 7. Here, the driving force is a parameter that depends on the amount of heat generated, based on factors such as the pulse generation rate of the pseudo-pulse generating circuit, the resistance of the heating circuit, the current flowing through the heating circuit, and the on / off time of the resistor. The greater the driving force, the greater the amount of heat generated.

[0061] Then, the control unit 7 drives the ASIC 43 with the determined driving force (step S14 ). The control unit 7 executes steps S13 and S14 for each ASIC 43 for which the measured value T is lower than the target value Ta.

[0062] The control unit 7 then determines whether a termination condition has been met (step S15). For example, the termination condition may be receipt of a termination instruction input by the operator using the input device 9. If the termination condition is not met (step S15: "No"), the control unit 7 returns the process to step S10. On the other hand, if the termination condition is met (step S15: "Yes"), the control unit 7 terminates the drive control.

[0063] As described above, by repeatedly executing steps S11 to S14 during the standby period, the temperature of each ASIC 43 approaches the target value Ta. Thus, according to this embodiment, temperature differences among the multiple ASICs 43 can be suppressed through drive control during the standby period. This minimizes temperature differences when imaging begins after the standby period ends, thus preventing degradation of tomographic images caused by differences in dark current noise and other factors.

[0064] Various modifications of the first embodiment will be described below.

[0065] [First Modification]

[0066] In the above embodiment, the control unit 7 performs drive control so that the temperatures of the plurality of ASICs 43 are at a single target value Ta. However, the target value Ta may be different for each ASIC 43. For example, the control unit 7 may store the temperature values ​​T measured by each temperature sensor 45 during calibration as target values ​​Ta, and perform drive control so that the temperature values ​​T of each ASIC 43 are close to the target values ​​Ta during the standby period.

[0067] For example, Figure 6 As shown, the control unit 7 performs phantom calibration as a calibration step (step S20). Phantom calibration is a process that generates correction data by performing imaging using a phantom with known concentration and transmission length, in order to obtain the concentration and transmission length of the subject H obtained through imaging. Phantom calibration is performed at the time of shipment of the radiographic apparatus 2 or during periodic maintenance.

[0068] The control unit 7 acquires the measurement value T of the temperature measured by each temperature sensor 45 during the phantom calibration (step S21 ) and stores each acquired measurement value T as a target value Ta in the storage device 11 (step S22 ).

[0069] During the standby period, the control unit 7 retrieves each target value Ta from the storage device 11 and performs the aforementioned drive control. This allows each ASIC 43 to approach the temperature used during calibration when imaging begins after the standby period. The target value Ta is not limited to the temperature used during phantom calibration; for example, it may also be the temperature used during air calibration performed by the user every morning.

[0070] [Second Modification]

[0071] In the above embodiment, the control unit 7 controls the operation of each ASIC 43 during the standby period so that the temperature approaches the target value Ta and maintains the temperature near the target value Ta. However, the control unit 7 may also predict the temperature change of each ASIC 43 during the standby period and control the operation based on the predicted temperature change. Furthermore, the control unit 7 may determine the standby period based on imaging plan information received from a RIS or other device via the communication device 12. For example, the imaging plan information includes the imaging time and duration in continuous imaging.

[0072] Figure 7 The following shows a flow of drive control by the control unit 7 according to the second modification: First, the control unit 7 acquires imaging plan information from the RIS or the like in advance (step S30), and determines a waiting period based on the acquired imaging plan information (step S31).

[0073] Next, the control unit 7 determines whether the currently-performing imaging has been completed (step S32). If the imaging has not been completed (step S32: No), the control unit 7 repeats this determination. If the imaging has been completed (step S32: Yes), the control unit 7 obtains the measured temperature value T of each ASIC 43 at the time of completion of the imaging from the temperature sensor 45 (step S33).

[0074] Next, the control unit 7 predicts the temperature change of each ASIC 43 during the standby period based on the measured values ​​T (step S34). The control unit 7 then determines the drive start time for each ASIC 43 based on the predicted temperature change (step S35). The control unit 7 then determines whether the drive start time has arrived for each ASIC 43 (step S36). If the drive start time has not arrived (step S36: "No"), the control unit 7 repeats this determination.

[0075] If the drive start time has arrived (step S36: YES), the control unit 7 drives the ASIC 43 (step S37). The control unit 7 then determines whether the end time of the standby period has arrived (step S38). If the end time has not arrived (step S38: NO), the control unit 7 returns the process to step S37 and continues driving. If the end time has arrived (step S38: YES), the control unit 7 ends driving.

[0076] Figure 8 An example of drive control according to the second modification example for one ASIC 43 is schematically shown. Figure 8 In this example, t1 is the end time of one imaging cycle, and t2 is the start time of the next imaging cycle. That is, the period from t1 to t2 is the standby period, and t2 is also the end time of the standby period. Furthermore, T1 is the measured temperature at the end time t1 of the imaging cycle. T2 is the temperature estimated to have been reached when the ASIC 43 was not driven during the standby period.

[0077] When the control unit 7 drives the ASIC 43 with a driving force P based on the predicted temperature change during the standby period, it estimates a drive start time ts at which the target value Ta will be reached at the end time t2 of the standby period. When the time elapsed from the end time t1 of imaging reaches the drive start time ts, the control unit 7 drives the ASIC 43 with the driving force P. By driving the ASIC 43 with a constant driving force P until the end time t2 of the standby period, the temperature of the ASIC 43 reaches the target value Ta at the end time t2.

[0078] [Third Modification]

[0079] In the second modification, the temperature change of each ASIC 43 during the standby period is predicted. Figure 9 As shown, when drive control is not being performed, the estimated temperature T2 reached at the end time t2 of the standby period may be higher than the target value Ta. For ASICs 43 whose estimated temperature T2 is higher than the target value Ta, the temperature at the end time t2 cannot be set to the target value Ta. Therefore, if any of the multiple estimated temperatures T2 is higher than the target value Ta, the temperature difference between each ASIC 43 becomes larger.

[0080] Therefore, in this variation, the control unit 7 calculates an estimated temperature T2 for each ASIC43 that is estimated to be reached when the standby period ends without drive control. When any of the multiple estimated temperatures T2 is higher than the target value Ta, the highest temperature among the multiple estimated temperatures T2 is used as the target value Ta for all ASIC43 to perform drive control.

[0081] Figure 10 The following shows a flow of drive control according to the third modification example by the control unit 7. The drive control according to this modification example differs from the drive control according to the second modification example only in that steps S40 and S41 are executed between steps S34 and S35.

[0082] In this modified example, after predicting the temperature changes of each ASIC 43 during the standby period in step S34, the control unit 7 determines whether there is an ASIC 43 with a T2 > Ta (step S40). If there is no ASIC 43 with a T2 > Ta (step S40: No), the control unit 7 transfers the process to step S35. If there is an ASIC 43 with a T2 > Ta (step S40: Yes), the control unit 7 sets the maximum estimated temperature T2 among the estimated temperatures T2 that are greater than the target value Ta as the target value Ta (step S41).

[0083] As described above, in this modification, even when any one of the plurality of estimated temperatures T2 is higher than the target value Ta, the maximum estimated temperature T2 is set to the target value Ta, thereby suppressing the temperature difference among the ASICs 43 .

[0084] [Second embodiment]

[0085] Figure 11 The structure of a radiographic apparatus 2a according to the second embodiment is schematically shown. The radiographic apparatus 2a includes multiple cooling fans 50 disposed near the X-ray detector 4. For example, the multiple cooling fans 50 are arranged so as to blow air toward the multiple detector modules 40 from the Z direction. Furthermore, the multiple cooling fans 50 are driven and controlled by a controller 7. The rest of the structure of the radiographic apparatus 2a is the same as that of the radiographic apparatus 2 according to the first embodiment. Furthermore, the radiographic apparatus 2a only needs to have at least one cooling fan 50.

[0086] In this embodiment, when any one of the multiple temperature measurement values ​​T measured for the multiple ASICs 43 exceeds the target value Ta, the control unit 7 drives at least one cooling fan 50. Furthermore, the control unit 7 controls the rotation of the at least one cooling fan 50 so that the temperature of each ASIC 43 approaches the target value Ta when the standby period ends.

[0087] Figure 12 The flowchart of the drive control performed by the control unit 7 according to the second embodiment is shown. The drive control according to this embodiment differs from the drive control according to the first embodiment only in that step S50 is added. In this embodiment, the control unit 7 determines whether each measured value T is lower than the target value Ta in step S12, and when any measured value T is higher than the target value Ta (step S12: "No"), drives at least one cooling fan 50 (step S50). For example, all cooling fans 50 are driven. At this time, the control unit 7 controls the rotation of the cooling fan 50 according to the difference between the measured value T and the target value Ta. Specifically, the greater the difference between the measured value T and the target value Ta, the more the control unit 7 increases the rotation speed of the cooling fan 50. Then, the control unit 7 transfers the processing to step S15.

[0088] Thus, in this embodiment, when the measured value T is lower than the target value Ta, the drive control of ASIC 43 is performed, and when the measured value T is higher than the target value Ta, the cooling fan 50 is driven to cool ASIC 43, thereby making the temperature of ASIC 43 closer to the target value Ta more accurately.

[0089] The second embodiment may also employ the second modification of the first embodiment to drive at least one cooling fan 50 when any of the plurality of estimated temperatures T2 exceeds the target value Ta. Furthermore, the first modification of the first embodiment may also be employed in the second embodiment.

[0090] Hereinafter, modifications common to the above-mentioned embodiments will be described.

[0091] In the above embodiments, the temperature sensor 45 is provided inside each ASIC 43, but the temperature sensor 45 may also be provided outside the ASIC 43. Figure 13 As shown, a plurality of temperature sensors 45 may be disposed in the container 4a housing the X-ray detector 4. The plurality of temperature sensors 45 are preferably disposed evenly in the X and Z directions. In this case, the control unit 7 may simply obtain the measured temperature value T of each ASIC 43 from the temperature sensor 45 disposed near each ASIC 43.

[0092] Furthermore, the temperature measuring device is not limited to being composed of a plurality of temperature sensors 45 , and may be a device capable of measuring the entire temperature of the X-ray detector 4 , such as a thermal imaging camera.

[0093] In the above embodiments, temperature sensor 45 measures the temperature of each ASIC 43. However, it is also possible to measure the temperature of one or more of the multiple components that make up the photon counting circuit 44 included in each ASIC 43. In other words, "measuring the temperature of a region where multiple circuit components are arranged" as used in this disclosure includes measuring the temperature of one or more of the multiple components that make up the circuit component. This is described in detail below.

[0094] Figure 14 The structure of the photon counting circuit 44 is shown. The photon counting circuit 44 includes an amplifier circuit 44A, a waveform shaping circuit 44B, a comparator circuit 44C, and a counter circuit 44D. These are a plurality of elements constituting the aforementioned circuit elements.

[0095] The amplifier circuit 44A is a circuit that amplifies the charge generated when an X-ray photon is incident on the semiconductor layer 42. The amplifier circuit 44A is connected to the upper electrode 42A formed in the semiconductor layer 42 and one of the lower electrodes 42B among the multiple lower electrodes 42B, integrates / amplifies the charge and outputs it as a pulse signal. The waveform shaping circuit 44B removes the noise of the pulse signal output from the amplifier circuit 44A and shapes it into an appropriate shape. The comparator circuit 44C has multiple comparators, each of which uses a different threshold value to compare the amplitude of the pulse signal shaped by the waveform shaping circuit 44B with the threshold value. In this way, the photon energy is classified into multiple energy bands. The counter circuit 44D includes multiple counters that individually count the number of photons corresponding to each different energy band and output a count signal.

[0096] With the above configuration, the photon counting circuit 44 performs high-precision energy discrimination and photon counting.

[0097] In each of the above-described embodiments, the temperature sensor 45 provided within each ASIC 43 may also measure the temperature of one of the amplifier circuit 44A, waveform shaping circuit 44B, comparator circuit 44C, and counter circuit 44D during standby. For example, the temperature sensor 45 may measure the temperature of the element with the largest temperature increase due to photon counting among the multiple elements. Alternatively, the temperature sensor 45 may measure the temperature of the element with the greatest temperature fluctuation affecting the photon counting output among the multiple elements. Furthermore, the temperature sensor 45 may measure the temperatures of two or more of the multiple elements. In this case, the average or maximum value of the two or more measured temperatures may be used as the measured temperature.

[0098] That is, in each of the above-described embodiments, the temperature sensor 45 may also be configured to measure the temperature of one or more of the multiple components comprising the photon counting circuit 44. In this case, the control unit 7 may also drive (i.e., idle drive) one or more of the multiple components comprising the photon counting circuit 44 with an analog signal to increase the temperature, thereby performing temperature control, similar to the first embodiment. Furthermore, similar to the second embodiment, the control unit 7 may also drive the cooling fan 50 to perform temperature control.

[0099] The photon counting circuit 44 is not limited to the above configuration and may also include an A / D converter that converts analog signals such as charge signals into digital signals. In this case, the temperature sensor 45 can measure the temperature of the A / D converter. Furthermore, the control unit 7 can also perform temperature control by driving the A / D converter with an analog signal (i.e., idle driving) to increase the temperature.

[0100] Furthermore, in the above-described embodiments, the components constituting the photon counting circuit 44 are described as being contained within each ASIC 43, but this is not limiting. For example, a discrete configuration may be employed in which the components constituting the photon counting circuit 44, such as the amplifier circuit 44A, waveform shaping circuit 44B, comparator circuit 44C, counter circuit 44D, and A / D converter, are combined into separate electronic components. Furthermore, a portion of these components may be contained within the ASIC 43, with the remainder being configured as electronic components outside the ASIC 43. Furthermore, a temperature sensor 45 may be used to detect the temperature of one or more of these electronic components. Furthermore, the control unit 7 may drive one or more of these electronic components using an analog signal (i.e., idle driving) to increase the temperature, thereby performing temperature control. Furthermore, if the photon counting circuit 44 includes an A / D converter, the A / D converter may also be a separate electronic component.

[0101] Furthermore, in the above-mentioned embodiments, X-rays are described as an example of radiation, but gamma rays may also be used as radiation.

[0102] Furthermore, in the above-described embodiment, various processors described below can be used as the hardware configuration of the control unit 7. These various processors include general-purpose processors (CPUs) that execute software (programs) and function as various processing units, as well as PLDs (Programmable Logic Devices) whose circuit configuration can be modified after manufacturing, such as FPGAs (Field-Programmable Gate Arrays), and processors (special-purpose circuits) with circuit configurations specifically designed to execute specific processing, such as ASICs.

[0103] Furthermore, the various processes described above may be executed by one of these various processors, or by a combination of two or more processors of the same or different types (e.g., multiple FPGAs or a combination of a CPU and an FPGA). Furthermore, multiple processing units may be configured by a single processor. As an example of configuring multiple processing units by a single processor, there is a method of using a processor that implements the functions of the entire system including multiple processing units on a single IC (Integrated Circuit) chip, such as an SoC (System on a Chip).

[0104] Based on the above description, the techniques described in the following supplementary notes can be grasped.

[0105] [Supplementary Note 1]

[0106] A radiographic apparatus 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, wherein:

[0107] The radiographic apparatus includes:

[0108] a plurality of circuit elements including a photon counting circuit for counting photons;

[0109] a temperature measuring device for measuring the temperature of a region where a plurality of the circuit elements are arranged; and

[0110] The processor adjusts the temperature of the plurality of circuit elements by controlling the driving of the plurality of circuit elements based on the temperature measured by the temperature measuring device during a period in which the photon counting circuit does not count photons, that is, during a standby period.

[0111] [Supplementary Note 2]

[0112] The radiographic apparatus according to Supplementary Note 1, wherein:

[0113] The temperature measuring device is composed of a plurality of temperature sensors.

[0114] [Supplementary Note 3]

[0115] The radiographic apparatus according to Supplementary Note 2, wherein:

[0116] Each of the plurality of temperature sensors is disposed inside each of the plurality of circuit elements.

[0117] [Supplementary Note 4]

[0118] The radiographic apparatus according to any one of Supplementary Notes 1 to 3, wherein:

[0119] The processor performs the following processing:

[0120] storing the temperature values ​​of each of the plurality of circuit elements measured by the temperature measuring device during calibration as target values;

[0121] During the standby period, the drive control is performed so that the measured value approaches the target value.

[0122] [Supplementary Note 5]

[0123] The radiographic apparatus according to any one of Supplementary Notes 1 to 3, wherein:

[0124] The processor performs the following processing:

[0125] predicting temperature changes of the plurality of circuit elements during the standby period;

[0126] The drive control is performed based on the predicted temperature change.

[0127] [Supplementary Note 6]

[0128] The radiographic apparatus according to Supplementary Note 5, wherein:

[0129] The processor performs the following processing:

[0130] Get photography program information;

[0131] Based on the acquired imaging plan information, a period from the completion of one imaging session to the start of the next imaging session is determined as the waiting period.

[0132] [Supplementary Note 7]

[0133] The radiographic apparatus according to Supplementary Note 5 or 6, wherein:

[0134] The processor performs the following processing:

[0135] The drive control is performed so that the temperature of each of the plurality of circuit elements reaches a target value when the standby period ends.

[0136] [Supplementary Note 8]

[0137] The radiographic apparatus according to Supplementary Note 7, wherein:

[0138] The processor performs the following processing:

[0139] determining, for each of the plurality of circuit elements, an estimated temperature that is estimated to be reached when the standby period ends without performing the drive control;

[0140] When any one of the plurality of estimated temperatures is higher than the target value, the drive control is performed using the highest temperature among the plurality of estimated temperatures as the target value.

[0141] [Supplementary Note 9]

[0142] The radiographic apparatus according to Supplementary note 1, further comprising at least one cooling fan for cooling the plurality of circuit elements.

[0143] [Supplementary Note 10]

[0144] The radiographic apparatus according to Supplementary Note 9, wherein:

[0145] The processor performs the following processing:

[0146] When any one of the plurality of measurement values ​​measured by the temperature measuring device is higher than a target value, at least one of the cooling fans is driven.

[0147] [Supplementary Note 11]

[0148] The radiographic apparatus according to Supplementary Note 10, wherein:

[0149] The processor performs the following processing:

[0150] The rotation of at least one of the cooling fans is controlled so that the temperatures of the plurality of circuit elements approach the target value when the standby period ends.

Claims

1. A radiographic apparatus 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, wherein: The radiographic apparatus includes: a plurality of circuit elements including a photon counting circuit for counting photons; a temperature measuring device for measuring the temperature of a region where a plurality of the circuit elements are arranged; and The processor adjusts the temperature of the plurality of circuit elements by controlling the driving of the plurality of circuit elements based on the temperature measured by the temperature measuring device during a period in which the photon counting circuit does not count photons, that is, during a standby period.

2. The radiographic apparatus according to claim 1, wherein The temperature measuring device is composed of a plurality of temperature sensors.

3. The radiographic apparatus according to claim 2, wherein: Each of the plurality of temperature sensors is disposed inside each of the plurality of circuit elements.

4. The radiographic apparatus according to claim 1, wherein The processor performs the following processing: storing the temperature values ​​of each of the plurality of circuit elements measured by the temperature measuring device during calibration as target values; During the standby period, the drive control is performed so that the measured value approaches the target value.

5. The radiographic apparatus according to claim 1, wherein The processor performs the following processing: predicting temperature changes of the plurality of circuit elements during the standby period; The drive control is performed based on the predicted temperature change.

6. The radiographic apparatus according to claim 5, wherein: The processor performs the following processing: Get photography program information; Based on the acquired imaging plan information, a period from the completion of one imaging session to the start of the next imaging session is determined as the waiting period.

7. The radiographic apparatus according to claim 5 or 6, wherein: The processor performs the following processing: The drive control is performed so that the temperature of each of the plurality of circuit elements reaches a target value when the standby period ends.

8. The radiographic apparatus according to claim 7, wherein: The processor performs the following processing: determining, for each of the plurality of circuit elements, an estimated temperature that is estimated to be reached when the standby period ends without performing the drive control; When any one of the plurality of estimated temperatures is higher than the target value, the drive control is performed using the highest temperature among the plurality of estimated temperatures as the target value. 9 . The radiographic apparatus according to claim 1 , further comprising at least one cooling fan for cooling the plurality of circuit elements.

10. The radiographic apparatus according to claim 9, wherein The processor performs the following processing: When any one of the plurality of measurement values ​​measured by the temperature measuring device is higher than a target value, at least one of the cooling fans is driven.

11. The radiographic apparatus according to claim 10, wherein: The processor performs the following processing: The rotation of at least one of the cooling fans is controlled so that the temperatures of the plurality of circuit elements approach the target value when the standby period ends.

12. A method for controlling a radiographic apparatus, the radiographic apparatus being a radiographic apparatus 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, the radiographic apparatus comprising: a plurality of circuit elements including a photon counting circuit for counting photons; a temperature measuring device for measuring the temperature of a region where a plurality of the circuit elements are arranged; and processor, where The processor performs a process comprising the following steps: During a standby period when the photon counting circuit does not count photons, the temperatures of the circuit elements are adjusted by controlling the driving of the circuit elements based on the temperature measured by the temperature measuring device.

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