Radiography apparatus and control method of radiography apparatus

Abstract

To provide a radiography apparatus which can suppress the temperature difference of multiple circuit elements including a photon counting circuit, and a control method of the radiography apparatus.SOLUTION: A radiography apparatus detects radiation emitted from a radiation source and generates a radiation image on the basis of an electric signal corresponding to the number of photons of the radiation, and the radiography apparatus includes a plurality of circuit elements having a photon counting circuit that counts the photons; a temperature measurement device that measures a temperature of a region where the plurality of circuit elements are arranged; 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, in a standby period that is a period in which the photon counting circuit does not count the photons.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The technology of the present disclosure relates to a radiation imaging apparatus and a method for controlling the radiation imaging apparatus. [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 a PCCT device, incident photons are converted into electric charges in a semiconductor layer, and the converted electric charges are counted by a photon counting circuit, thereby counting photons. It is known that such photon-counting detectors generate heat as they count photons, and the amount of heat generated varies depending on the counting rate (see, for example, Patent Document 1).

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

[0005] [Patent Document 1] Japanese Patent Application Publication No. 2018-143575 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the technology described in Patent Document 1 does not take into consideration the standby period during which no image is captured and the photon counting circuit does not count photons. A photon counting detector has an array of circuit elements, each including a photon counting circuit, and since the counting rate during image capture differs for each photon counting circuit, the temperature at the end of image capture differs for each circuit element. For example, the counting rate of the photon counting circuit will be higher in circuit elements located in an area of ​​the subject where the radiation absorption rate is low and the amount of radiation transmitted is high.

[0007] For this reason, during the standby period, the temperature of each circuit element may differ significantly. When imaging is performed in such a state where the temperature of each circuit element differs significantly, the technology described in Patent Document 1 cannot suppress the temperature difference between each circuit element because it controls the amount of heat generated according to the counting rate. The temperature difference between each circuit element results in differences in dark current noise, etc., which causes degradation such as unevenness in the tomographic image.

[0008] Therefore, the technology according to the present disclosure provides a radiation imaging apparatus and a method for controlling a radiation imaging apparatus that can suppress the temperature difference among a plurality of circuit elements including a photon counting circuit. [Means for solving the problem]

[0009] A radiographic imaging device according to the disclosed technique 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 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 in which 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 measurement value measured by the temperature measuring device during a standby period in which the photon counting circuit does not count photons.

[0010] The temperature measuring device is preferably 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] The processor preferably stores the measured values ​​of the temperatures of the plurality of circuit elements measured by the temperature measuring device during calibration as target values, and performs drive control during the standby period so that the measured values ​​approach the target values.

[0013] It is also preferable that the processor predicts temperature changes of the plurality of circuit elements during the standby period and performs drive control based on the predicted temperature changes.

[0014] It is preferable that the processor acquires imaging plan information and, based on the acquired imaging plan information, specifies a period from the end of one imaging until the start of the next imaging as the waiting period.

[0015] The processor preferably controls the driving of the plurality of circuit elements so that the temperature of each of the circuit elements reaches the target value at the end of the waiting period.

[0016] For each of the plurality of circuit elements, the processor preferably determines an estimated temperature that is estimated to be reached at the end of the standby period if no drive control is performed, and if any of the plurality of estimated temperatures is higher than a target value, preferably performs drive control using the highest temperature of the plurality of estimated temperatures as the target value.

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

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

[0019] Preferably, the processor controls the rotation of the at least one cooling fan so that the temperatures of the plurality of circuit elements approach the target values ​​at the end of the waiting period.

[0020] A control method for a radiographic imaging apparatus according to the disclosed technology is a radiographic imaging 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 control method for a radiographic imaging apparatus comprising: a plurality of circuit elements having a photon counting circuit that counts photons; a temperature measuring device that measures the temperature of an area in which the plurality of circuit elements are arranged; and a processor, wherein the processor performs processing that includes adjusting the temperature of the plurality of circuit elements by controlling the drive of the plurality of circuit elements based on the temperature measurement value measured by the temperature measuring device during a standby period in which the photon counting circuit does not count photons. [Effects of the Invention]

[0021] According to the technique of the present disclosure, it is possible to provide a radiation imaging apparatus and a method for controlling a radiation imaging apparatus that are capable of suppressing the temperature difference between a plurality of circuit elements including a photon counting circuit. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a diagram schematically showing the configuration of a radiation imaging apparatus according to a first embodiment. [Figure 2] FIG. 1 is a perspective view showing a schematic configuration of an X-ray detector. [Figure 3] FIG. 2 is a diagram schematically illustrating a configuration example of a detector module. [Figure 4] FIG. 4 is a diagram showing a flow of drive control by a control unit according to the first embodiment. [Figure 5] FIG. 10 is a diagram showing the relationship between the measured temperature value and the driving force. [Figure 6] FIG. 10 is a diagram illustrating an example of a calibration flow. [Figure 7] FIG. 10 is a diagram showing a flow of drive control by a control unit according to a second modified example. [Figure 8] FIG. 10 is a diagram schematically illustrating an example of drive control for one ASIC according to a second modified example. [Figure 9] FIG. 10 is a diagram illustrating a problem of the second modified example. [Figure 10]FIG. 11 is a diagram showing a flow of drive control by a control unit according to a third modified example. [Figure 11] FIG. 10 is a diagram schematically showing the configuration of a radiation imaging apparatus according to a second embodiment. [Figure 12] FIG. 10 is a diagram showing a flow of drive control by a control unit according to the second embodiment. [Figure 13] FIG. 10 is a diagram illustrating another example of the arrangement of a plurality of temperature sensors. [Figure 14] FIG. 2 is a diagram illustrating the configuration of a photon counting circuit. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the technology of the present disclosure will be described with reference to the drawings. The radiographic imaging apparatus of the present disclosure is applied 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 of the radiation. In this embodiment, the case where the radiation is X-rays will be described as an example.

[0024] [First embodiment] 1 schematically shows the configuration of a radiographic apparatus 2 according to the first embodiment. 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 placing the bed 6 on which the subject H is placed. The gantry 5 also includes a rotating plate 52 fixed at a position where the X-ray source 3 and the X-ray detector 4 face each other, and a drive mechanism (not shown) for rotating the rotating plate 52.

[0025] 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.

[0026] 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 generated X-rays onto the subject H. 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.

[0027] 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.

[0028] 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 the 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.

[0029] 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. The counting signal corresponds to the "electrical signal corresponding to the number of photons" according to the technology of the present disclosure.

[0030] 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 flow of current due to the incidence of photons on the semiconductor layer 42. The temperature change of the ASIC 43 when X-rays are incident depends on the photon counting rate of the photon counting circuit 44. The multiple temperature sensors 45 provided in the radiation imaging apparatus 2 are an example of a "temperature measuring device" according to the technology of the present disclosure.

[0031] 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 irradiation 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 counting signal output from the photon counting circuit 44 of the ASIC 43 and a temperature measurement value output from the temperature sensor 45.

[0032] The image processing unit 8 is an image processing processor that generates a tomographic image (also referred to as 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. The tomographic image is an example of a "radiation image" according to the technology of the present disclosure.

[0033] 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.

[0034] 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.

[0035] Furthermore, the ASIC 43 is configured so that its temperature can be changed by being driven and controlled by the control unit 7 during a standby period when the photon counting circuit 44 is not counting photons. For example, the control unit 7 increases the temperature of the ASIC 43 by idle driving the photon counting circuit 44 to increase power consumption. Specifically, the ASIC 43 is provided with a spurious pulse generating circuit that generates spurious pulses to cause the photon counting circuit 44 to perform spurious counting, and the control unit 7 drives the spurious pulse generating circuit to cause the ASIC 43 to generate heat. The control unit 7 can control the amount of heat generation by controlling the generation rate of pulses generated by the spurious pulse generating circuit. The pulse generation rate refers to the number of pulses generated per unit time.

[0036] Instead of the spurious pulse generating circuit, a heat generating circuit that generates heat itself may be provided within the ASIC 43. For example, the heat generating circuit is a circuit including a resistor. The control unit 7 drives and controls the heat generating circuit to raise the temperature of the ASIC 43. The control unit 7 can control the amount of heat generated by controlling the resistance of the heat generating circuit, the current flowing through the heat generating circuit, the ON / OFF time of the resistor, etc.

[0037] The configuration and control method for changing the temperature of the ASIC 43 as described above are known from Japanese Patent Application Laid-Open No. 2018-143575.

[0038] 3 schematically illustrates an exemplary configuration of the detector module 40. For example, the detector module 40 includes four ASICs 43 mounted on a holding 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.

[0039] Since the photon counting rate during imaging differs for each photon counting circuit 44 within the ASIC 43, the temperature at the end of imaging differs for each ASIC 43. For example, in an ASIC 43 located in an area where the X-ray absorption rate of the subject H is low and the amount of X-ray transmission is high, the counting rate by the photon counting circuit 44 will be high. As a result, temperature differences will occur among the multiple ASICs 43 during the standby period of the radiation imaging device 2. During the standby period, photon counting is not performed, so the temperature of each ASIC 43 decreases, but the temperature differences among the ASICs 43 are not eliminated. Such temperature differences will degrade the tomographic image.

[0040] The control unit 7 adjusts the temperature of each ASIC 43 by controlling the driving of each ASIC 43 to suppress temperature differences among the ASICs 43 during the standby period. The standby period is a period during which the radiation imaging apparatus 2 does not perform imaging, and the photon counting circuit 44 does not count photons as described above. For example, the standby period is the period from the end of one imaging session to the start of the next imaging session.

[0041] 4 shows the flow of drive control by the control unit 7 according to the first embodiment. In this embodiment, the control unit 7 controls the drive of each ASIC 43 during the standby period so that the temperature of each ASIC 43 reaches a predetermined target value Ta.

[0042] First, the control unit 7 determines whether or not it is a standby period (step S10). If it is not a standby period (step S10: NO), the control unit 7 shifts the process to step S15. On the other hand, if it is a standby period (step S10: YES), the control unit 7 acquires the measured value T of the temperature of each ASIC 43 from each temperature sensor 45 (step S11).

[0043] 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 proceeds 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 a driving force for driving the ASIC 43 based on the temperature difference between the measured value T and the target value Ta (step S13). As shown in FIG. 5, the lower the measured value T is from the target value Ta, the greater the driving force the control unit 7 determines. Here, the driving force is a parameter that depends on the amount of heat generated, such as the pulse generation rate by the spurious pulse generation circuit, the resistance of the heat generating circuit, the current flowing through the heat generating circuit, and the ON / OFF time of the resistor. The greater the driving force, the greater the amount of heat generated.

[0044] 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 whose measurement value T is lower than the target value Ta.

[0045] Thereafter, the control unit 7 determines whether or not a termination condition is satisfied (step S15). For example, the termination condition is that a termination instruction input by an operator using the input device 9 has been accepted. If the termination condition is not satisfied (step S15: NO), the control unit 7 returns the process to step S10. On the other hand, if the termination condition is satisfied (step S15: YES), the control unit 7 terminates the drive control.

[0046] As described above, steps S11 to S14 are repeatedly executed during the standby period, causing the temperature of each ASIC 43 to approach the target value Ta. In this way, according to this embodiment, the temperature difference between the multiple ASICs 43 can be suppressed by drive control during the standby period. As a result, when the standby period ends and imaging begins, the temperature difference is suppressed, and degradation of the tomographic image due to differences in dark current noise, etc. is suppressed.

[0047] Various modifications of the first embodiment will be described below.

[0048] [First Modification] In the above embodiment, the control unit 7 performs drive control so that the temperatures of the plurality of ASICs 43 become one target value Ta, but the target value Ta may be different for each ASIC 43. For example, the control unit 7 may store the measured values ​​T of the temperatures measured by each temperature sensor 45 during calibration as the target values ​​Ta, and perform drive control so that the measured values ​​T of the temperatures of each ASIC 43 approach the target value Ta during the standby period.

[0049] 6, the control unit 7 performs phantom calibration as the calibration (step S20). Phantom calibration is a process of generating correction data by performing imaging using a phantom whose density and transmission length are known, in order to configure the density and transmission length of the subject H obtained by imaging. Phantom calibration is performed when the radiation imaging apparatus 2 is shipped, during periodic inspection, etc.

[0050] The control unit 7 acquires the temperature measurement value T measured by each temperature sensor 45 during phantom calibration (step S21). Then, the control unit 7 stores each acquired measurement value T as a target value Ta in the storage device 11 (step S22).

[0051] During the standby period, the control unit 7 acquires each target value Ta from the storage device 11 and performs the above-described drive control. This allows each ASIC 43 to approach the temperature at the time of calibration when imaging begins after the standby period ends. Note that the target value Ta is not limited to the temperature at the time of phantom calibration, and may be, for example, the temperature at the time of air calibration performed by the user every morning.

[0052] [Second Modification] In the above embodiment, the control unit 7 controls the temperature of each ASIC 43 to approach the target value Ta during the standby period and maintain the temperature near the target value Ta, but the control unit 7 may predict a temperature change of each ASIC 43 during the standby period and control the drive based on the predicted temperature change. The control unit 7 may also specify the standby period based on imaging plan information acquired from the RIS or the like via the communication device 12. For example, the imaging plan information includes imaging timing and imaging time for continuous imaging.

[0053] 7 shows a flow of drive control by the control unit 7 according to the second modified example. First, the control unit 7 acquires imaging plan information from the RIS or the like in advance (step S30), and specifies a standby period based on the acquired imaging plan information (step S31).

[0054] Next, the control unit 7 determines whether the current imaging has ended (step S32), and if the imaging has not ended (step S32: NO), repeats the determination. If the imaging has ended (step S32: YES), the control unit 7 acquires the measurement value T of each ASIC 43 at the time of the imaging end from the temperature sensor 45 (step S33).

[0055] Next, the control unit 7 predicts a temperature change of each ASIC 43 during the standby period based on each measurement value T (step S34). Then, the control unit 7 determines a drive start time for each ASIC 43 based on the predicted temperature change (step S35). Thereafter, the control unit 7 determines whether the drive start time has arrived for each ASIC 43 (step S36), and if the drive start time has not arrived (step S36: NO), repeats the determination.

[0056] If the drive start time has arrived (step S36: YES), the control unit 7 drives the ASIC 43 (step S37). Then, the control unit 7 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.

[0057] FIG. 8 shows an example of drive control according to the second modification for one ASIC 43. In FIG. 8, t1 is the end time of one image capture, and t2 is the start time of the next image capture. That is, the period from t1 to t2 is a 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 image capture. T2 is the temperature that is estimated to be reached if the ASIC 43 is not driven during the standby period.

[0058] Based on a prediction of temperature change during the standby period, the control unit 7 determines a drive start time ts at which the target value Ta is estimated to be reached at end time t2 of the standby period when the ASIC 43 is driven with drive force P. When the elapsed time from end time t1 of shooting reaches drive start time ts, the control unit 7 drives the ASIC 43 with drive force P. By driving the ASIC 43 with a constant drive force P until end time t2 of the standby period, the temperature of the ASIC 43 reaches the target value Ta at end time t2.

[0059] [Third Modification] In the second modification, the temperature change of each ASIC 43 during the standby period is predicted. However, as shown in FIG. 9, if drive control is not performed, the estimated temperature T2 estimated to be reached at the end time t2 of the standby period may be higher than the target value Ta. For an ASIC 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 large.

[0060] Therefore, in this modified example, the control unit 7 calculates an estimated temperature T2 for each ASIC 43 that is estimated to be reached at the end of the standby period if no drive control is performed, and if any of the multiple estimated temperatures T2 is higher than the target value Ta, it performs drive control using the highest temperature among the multiple estimated temperatures T2 as the target value Ta for all ASICs 43.

[0061] 10 shows the flow of drive control by the control unit 7 according to the third modified example. The drive control according to this modified example differs from the drive control according to the second modified example only in that steps S40 and S41 are executed between steps S34 and S35.

[0062] In this modification, the control unit 7 predicts the temperature change of each ASIC 43 during the standby period in step S34, and then determines whether there is any ASIC 43 for which T2>Ta (step S40). If there is no ASIC 43 for which T2>Ta (step S40: NO), the control unit 7 proceeds to step S35. If there is an ASIC 43 for which T2>Ta (step S40: YES), the control unit 7 sets the maximum estimated temperature T2 among the estimated temperatures T2 greater than the target value Ta as the target value Ta (step S41).

[0063] In this manner, in this modified example, even if any of the multiple estimated temperatures T2 is higher than the target value Ta, the maximum estimated temperature T2 is set as the target value Ta, thereby suppressing the temperature difference between each ASIC 43.

[0064] [Second embodiment] FIG. 11 shows a schematic configuration of a radiographic apparatus 2a according to the second embodiment. In the radiographic apparatus 2a, a plurality of cooling fans 50 are arranged near the X-ray detector 4. For example, the plurality of cooling fans 50 are arranged so as to blow air from the Z direction toward the plurality of detector modules 40. The plurality of cooling fans 50 are driven and controlled by a control unit 7. The other configuration of the radiographic apparatus 2a is the same as that of the radiographic apparatus 2 according to the first embodiment. It is sufficient that the radiographic apparatus 2a is provided with at least one cooling fan 50.

[0065] In this embodiment, when any one of the measured values ​​T of the temperatures measured for the plurality of ASICs 43 is higher than the target value Ta, the control unit 7 drives at least one cooling fan 50. Furthermore, the control unit 7 controls the rotation of at least one cooling fan 50 so that the temperature of each ASIC 43 approaches the target value Ta at the end of the standby period.

[0066] FIG. 12 shows the flow of drive control by the control unit 7 according to the second embodiment. 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 in step S12 whether each measurement value T is lower than the target value Ta. If any measurement value T is higher than the target value Ta (step S12: NO), at least one cooling fan 50 is driven (step S50). For example, all cooling fans 50 are driven. At this time, the control unit 7 controls the rotation of the cooling fans 50 according to the difference between the measurement value T and the target value Ta. Specifically, the control unit 7 increases the rotation speed of the cooling fans 50 as the difference between the measurement value T and the target value Ta increases. After this, the control unit 7 proceeds to step S15.

[0067] In this way, in this embodiment, when the measured value T is lower than the target value Ta, the ASIC 43 is controlled to be driven, and when the measured value T is higher than the target value Ta, the cooling fan 50 is driven to cool the ASIC 43, thereby enabling the temperature of the ASIC 43 to be brought closer to the target value Ta with greater accuracy.

[0068] Note that the second modified example of the first embodiment may be applied to the second embodiment, and at least one cooling fan 50 may be driven when any one of the multiple estimated temperatures T2 is higher than the target value Ta. Also, the first modified example of the first embodiment may be applied to the second embodiment.

[0069] Below, a description will be given of modifications common to the above embodiments.

[0070] 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, as shown in FIG. 13 , a plurality of temperature sensors 45 may be disposed in a container 4a that houses 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 acquire the measured value T of the temperature of each ASIC 43 from the temperature sensor 45 disposed near each ASIC 43.

[0071] Furthermore, the temperature measurement device is not limited to a configuration including a plurality of temperature sensors 45, but may be one that can measure the temperature of the entire X-ray detector 4, such as a thermography camera.

[0072] In each of the above embodiments, the temperature sensor 45 measures the temperature of each ASIC 43, but it may also measure the temperature of one or more of the multiple elements constituting the photon counting circuit 44 included in each ASIC 43. That is, "measuring the temperature of an area where multiple circuit elements are arranged" according to the present disclosure includes measuring the temperature of one or more of the multiple elements constituting the circuit element. More specifically, this will be described below.

[0073] 14 shows the configuration of the photon counting circuit 44. 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 multiple elements that make up the above-mentioned circuit elements.

[0074] The amplifier circuit 44A is a circuit that amplifies electric charges generated when X-ray photons are incident on the semiconductor layer 42. The amplifier circuit 44A is connected to an upper electrode 42A formed on the semiconductor layer 42 and one lower electrode 42B out of the plurality of lower electrodes 42B, and integrates and amplifies the electric charges to output them as a pulse signal.

[0075] The waveform shaping circuit 44B removes noise from the pulse signal output from the amplifier circuit 44A and shapes it into an appropriate shape. The comparator circuit 44C has multiple comparators, each using a different threshold value to compare the amplitude of the pulse signal shaped by the waveform shaping circuit 44B with the threshold value. This classifies the photon energy into multiple energy bands. The counter circuit 44D includes multiple counters, each of which individually counts the number of photons corresponding to a different energy band and outputs a count signal.

[0076] With the above configuration, the photon counting circuit 44 performs highly accurate energy discrimination and photon counting.

[0077] In each of the above embodiments, the temperature sensor 45 provided inside each ASIC 43 may measure the temperature of one of the amplifier circuit 44A, the waveform shaping circuit 44B, the comparator circuit 44C, and the counter circuit 44D during the standby period. For example, the temperature sensor 45 may measure the temperature of an element among the multiple elements that experiences the largest temperature rise due to photon counting. Alternatively, the temperature sensor 45 may measure the temperature of an element among the multiple elements that is most affected by temperature fluctuations on the photon counting output. 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.

[0078] That is, in each of the above embodiments, the object of temperature measurement by the temperature sensor 45 may be one or more of the multiple elements constituting the photon counting circuit 44. In this case, the control unit 7 may perform temperature adjustment by driving one or more of the multiple elements constituting the photon counting circuit 44 using a pseudo signal (i.e., idling) to raise the temperature, as in the first embodiment. Furthermore, the control unit 7 may perform temperature adjustment by driving the cooling fan 50, as in the second embodiment.

[0079] Furthermore, the photon counting circuit 44 is not limited to the above configuration and may be configured to include an A / D converter that converts an analog signal such as a charge signal into a digital signal. In this case, the temperature sensor 45 may measure the temperature of the A / D converter. Furthermore, the control unit 7 may adjust the temperature by driving the A / D converter using a pseudo signal (i.e., idling) to increase the temperature.

[0080] In the above embodiments, the elements constituting the photon counting circuit 44 are described as being included within each ASIC 43. However, this is not limiting. For example, the elements constituting the photon counting circuit 44, such as the amplifier circuit 44A, the waveform shaping circuit 44B, the comparator circuit 44C, the counter circuit 44D, and the A / D converter, may be configured as discrete electronic components. Alternatively, some of these elements may be included within the ASIC 43, with the remaining elements configured as electronic components outside the ASIC 43. Furthermore, the temperature sensor 45 may be used to detect the temperature of one or more of these electronic components. Additionally, the control unit 7 may adjust the temperature by driving one or more of these electronic components using a pseudo signal (i.e., idle driving) to increase the temperature. Similarly, when the photon counting circuit 44 includes an A / D converter, the A / D converter may be configured as a separate electronic component.

[0081] Furthermore, in the above embodiments, X-rays are used as radiation, but gamma rays may also be used as radiation.

[0082] In the above embodiment, the hardware structure of the control unit 7 can use various processors as shown below. The various processors include a CPU, which is a general-purpose processor that executes software (programs) and functions as various processing units, as well as dedicated electrical circuits such as a PLD (Programmable Logic Device) whose circuit configuration can be changed after manufacture, such as an FPGA (Field-Programmable Gate Array), and an ASIC, which is a processor with a circuit configuration designed specifically for executing specific processing.

[0083] 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). Furthermore, 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).

[0084] From the above description, the technology described in the following supplementary paragraphs can be understood.

[0085] [Additional note 1] A radiographic imaging 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, a plurality of circuit elements each having a photon counting circuit for counting photons; a temperature measuring device that measures the temperature of an area in which a plurality of the circuit elements are arranged; a processor that adjusts the temperatures 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 standby period in which the photon counting circuit does not count photons; A radiographic imaging device comprising: [Additional note 2] The temperature measuring device is composed of a plurality of temperature sensors. Item 1. A radiographic imaging apparatus according to claim 1. [Additional note 3] Each of the plurality of temperature sensors is provided inside each of the plurality of circuit elements. Item 2. A radiographic imaging apparatus according to claim 2. [Additional note 4] The processor: storing the measured values ​​of the temperatures of the plurality of circuit elements measured by the temperature measuring device during calibration as target values; The drive control is performed so that the measurement value approaches the target value during the waiting period. Item 3. The radiographic imaging apparatus according to any one of items 1 to 3. [Additional note 5] The processor: predicting temperature changes of the plurality of circuit elements during the standby period; The drive control is performed based on the predicted temperature change. Item 3. The radiographic imaging apparatus according to any one of items 1 to 3. [Additional note 6] The processor: Acquire shooting plan information, Based on the acquired imaging plan information, a period from the end of one imaging to the start of the next imaging is specified as the waiting period. Item 6. The radiographic imaging apparatus according to claim 5. [Additional note 7] The processor: The drive control is performed so that the temperature of each of the plurality of circuit elements reaches a target value at the end of the standby period. Item 7. The radiographic imaging apparatus according to item 5 or 6. [Additional note 8] The processor: determining an estimated temperature that is estimated to be reached at the end of the standby period if the drive control is not performed for each of the plurality of circuit elements; When any one of the plurality of estimated temperatures is higher than the target value, the highest temperature among the plurality of estimated temperatures is set as the target value and the drive control is performed. 8. The radiographic imaging apparatus according to claim 7. [Additional note 9] At least one cooling fan for cooling the plurality of circuit elements Item 1. A radiographic imaging apparatus according to claim 1. [Additional Note 10] The processor: 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. 10. The radiographic imaging apparatus according to claim 9. [Additional Note 11] The processor: and controlling rotation of at least one of the cooling fans so that the temperatures of the plurality of circuit elements approach the target values ​​at the end of the waiting period. Item 11. The radiographic imaging apparatus according to claim 10. [Explanation of symbols]

[0086] 2,2a Radiography equipment 3 X-ray source 4 X-ray detector 4a Container 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 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 board 50 Cooling Fan 51 Opening 52 Rotating Plate H Subject

Claims

1. A radiographic imaging 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, a plurality of circuit elements each having a photon counting circuit for counting photons; a temperature measuring device that measures the temperature of an area in which a plurality of the circuit elements are arranged; a processor that adjusts the temperatures 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 standby period in which the photon counting circuit does not count photons; A radiographic imaging device comprising:

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

3. Each of the plurality of temperature sensors is provided inside each of the plurality of circuit elements. The radiographic imaging apparatus according to claim 2 .

4. The processor: storing the measured values ​​of the temperatures of the plurality of circuit elements measured by the temperature measuring device during calibration as target values; The drive control is performed so that the measurement value approaches the target value during the waiting period. The radiographic apparatus according to claim 1 .

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

6. The processor: Acquire shooting plan information, Based on the acquired imaging plan information, a period from the end of one imaging to the start of the next imaging is specified as the waiting period. The radiographic apparatus according to claim 5 .

7. The processor: The drive control is performed so that the temperature of each of the plurality of circuit elements reaches a target value at the end of the standby period.

7. The radiographic imaging apparatus according to claim 5.

8. The processor: determining an estimated temperature that is estimated to be reached at the end of the standby period if the drive control is not performed for each of the plurality of circuit elements; When any one of the plurality of estimated temperatures is higher than the target value, the highest temperature among the plurality of estimated temperatures is set as the target value and the drive control is performed. The radiographic imaging apparatus according to claim 7 .

9. At least one cooling fan for cooling the plurality of circuit elements The radiographic apparatus according to claim 1 .

10. The processor: 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. The radiographic apparatus according to claim 9 .

11. The processor: 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 values ​​at the end of the waiting period. The radiographic imaging apparatus according to claim 10.

12. A radiographic imaging 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, a plurality of circuit elements each having a photon counting circuit for counting photons; a temperature measuring device that measures the temperature of an area in which a plurality of the circuit elements are arranged; a processor; A method for controlling a radiation imaging apparatus comprising: the processor: During a standby period in which the photon counting circuit does not count photons, the temperature of the plurality of circuit elements is adjusted by controlling the driving of the plurality of circuit elements based on the temperature measured by the temperature measuring device. A method for controlling a radiation imaging apparatus that executes a process including the steps of:

Images