Radiation detectors and nuclear medicine diagnostic devices

Abstract

To properly compensate for influence of temperature change on a radiation detector.SOLUTION: A radiation detector according to an embodiment includes a sensor unit, an A / D conversion unit, an acquisition unit, and an output control unit. The sensor unit outputs a pulse signal based on entrance of radiation. The A / D conversion unit generates digital data by A / D-converting the pulse signal. The acquisition unit acquires temperature information of the A / D conversion unit. The output control unit outputs digital data compensated based on the temperature information.SELECTED DRAWING: Figure 1

Description

Technical Field

[0005] , , ,

[0001] The embodiments disclosed in this specification and the drawings relate to radiation detectors and nuclear medicine diagnostic devices.

Background Art

[0002] Conventionally, as radiation detectors for nuclear medicine diagnostic devices such as positron emission computed tomography (PET) devices and radiation diagnostic devices such as photon counting computed tomography (PCCT) devices, silicon photomultiplier (SiPM)-based radiation detectors are known.

[0003] Analog signal processing in radiation detectors is known to be affected by temperature. Therefore, when a temperature change occurs in the radiation detector due to effects such as non-uniform heat dissipation or cooling, changes in the ambient environment, etc., there has been a problem that the output values of energy information and time information change.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] One of the problems to be solved by the embodiments disclosed in this specification, etc. is to appropriately compensate for the influence of temperature changes in the radiation detector. However, the problems to be solved by the embodiments disclosed in this specification and the drawings are not limited to the above problems. The problems corresponding to each configuration shown in the embodiments described later can also be regarded as other problems.

Means for Solving the Problems

[0006] The radiation detector according to this embodiment comprises a sensor unit, an A / D conversion unit, an acquisition unit, and an output control unit. The sensor unit outputs a pulse signal based on the incidence of radiation. The A / D conversion unit generates digital data by performing A / D conversion on the pulse signal. The acquisition unit acquires temperature information from the A / D conversion unit. The output control unit outputs compensated digital data based on the temperature information. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 shows an example of the configuration of a positron emission computed tomography (PET) apparatus according to an embodiment. [Figure 2] Figure 2 shows an example of the configuration of a detector unit according to the embodiment. [Figure 3] Figure 3 is a diagram illustrating the temperature compensation according to this embodiment. [Figure 4] Figure 4 is a diagram illustrating the temperature compensation according to the embodiment. [Figure 5] Figure 5 is a diagram illustrating the temperature compensation according to the embodiment. [Figure 6] Figure 6 is a flowchart showing an example of the output control process flow according to the embodiment. [Modes for carrying out the invention]

[0008] The radiation detectors and nuclear medicine diagnostic devices according to each embodiment will be described below with reference to the drawings. In the following description, components having the same or substantially the same function as those previously described in the drawings will be denoted by the same reference numerals, and will be described again only when necessary. Furthermore, even when representing the same part, the dimensions and proportions may differ between drawings. In addition, for example, from the viewpoint of ensuring the readability of the drawings, reference numerals may be denoted only for major or representative components in the description of each drawing, and reference numerals may not be denoted for components having the same or substantially the same function.

[0009] (First embodiment) Figure 1 shows an example of the configuration of a positron emission computed tomography (PET) apparatus 100 according to an embodiment. For example, as shown in Figure 1, the PET apparatus 100 has a rigging device 10 and a console device 20.

[0010] The rig 10 detects annihilation gamma rays emitted when positrons emitted from a tracer administered to a subject P annihilate with electrons, and collects count information by counting the detected annihilation gamma rays. Here, the rig 10 has a cylindrical opening formed to penetrate the rig 10 horizontally. The rig 10 detects annihilation gamma rays emitted from the subject P placed in the opening. In the following description, the direction along the axis of the cylindrical opening of the rig 10 is defined as the Z-axis direction. The horizontal direction perpendicular to the Z-axis direction is defined as the X-axis direction. The vertical direction perpendicular to both the Z-axis direction and the X-axis direction is defined as the Y-direction.

[0011] Specifically, the support structure 10 includes a top plate 11, a bed 12, a bed drive mechanism 13, and a PET detector 14.

[0012] The top plate 11 is a bed on which the subject P is placed. For example, the top plate 11 is formed in the shape of a rectangular flat plate and is positioned so that its longitudinal direction is parallel to the Z-axis direction.

[0013] The bed 12 supports the top plate 11 so that it can move in the X-axis, Y-axis, and Z-axis directions.

[0014] The bed drive mechanism 13 is located inside or outside the bed 12 and moves the top plate 11 supported by the bed 12. For example, when imaging of a subject P is performed, the bed drive mechanism 13 moves the top plate 11 on which the subject P is placed to the opening of the stand device 10. For example, the bed drive mechanism 13 moves the top plate 11 on the bed 12 while the position of the bed 12 is fixed. Alternatively, for example, the bed drive mechanism 13 may include a moving base and move the top plate 11 together with the bed 12 on the moving base.

[0015] The PET detector 14 detects annihilation gamma rays emitted from the subject P. The PET detector 14 then generates counting information including the detection location, energy value, and detection time of the detected annihilation gamma rays, and transmits the generated counting information to the console device 20.

[0016] Specifically, the PET detector 14 includes a plurality of detector units 14a arranged in a ring shape around the Z-axis so as to surround an opening formed in the mounting device 10, and each detector unit 14a detects annihilation gamma rays and generates counting information.

[0017] The detector unit 14a is, for example, a photon counting type or Anger type detector, and includes a scintillator, a photodetector, and a light guide.

[0018] A scintillator converts the gamma rays emitted from positrons in the sample P into scintillation light. For example, a scintillator is formed from a scintillator crystal suitable for energy measurement, such as LaBr3, LYSO, LSO, LGSO, BGO, GAGG, or LuAG. Alternatively, the scintillator can be arranged in two dimensions.

[0019] The photodetector detects the scintillation light output from the scintillator and converts it into an analog signal. The photodetector is constituted by, for example, a SiPM (Silicon Photomultiplier), but may be constituted by other photomultiplier tubes such as a PMT (Photomultiplier).

[0020] The light guide is formed of a plastic material or the like having excellent light transmittance, and transmits the scintillation light output from the scintillator to the photodetector.

[0021] Note that the detector unit 14a may be a non-anger type detector in which the scintillator and the photodetector are optically joined one-to-one and does not have a light guide. Alternatively, for example, the detector unit 14a may be a direct conversion type detector using a semiconductor such as CZT, CdTe, Ge, Si, etc., instead of an indirect conversion type detector using a scintillator.

[0022] And the detector unit 14a generates count information including the detection position, energy value, and detection time of the annihilation gamma rays based on the analog signal output from the photodetector.

[0023] For example, the detector unit 14a identifies a plurality of photodetectors that convert scintillation light into an analog signal at the same timing. Then, the detector unit 14a identifies the position of the scintillator where the annihilation gamma rays are incident as the detection position of the annihilation gamma rays. For example, the detector unit 14a performs a centroid calculation based on the position of the photodetector and the intensity of the analog signal to identify the position of the scintillator where the annihilation gamma rays are incident. Alternatively, for example, when the element sizes of the scintillator and the photodetector correspond to each other, the detector unit 14a may identify the position of the scintillator corresponding to the photodetector that has obtained an output as the position of the scintillator where the annihilation gamma rays are incident.

[0024] Alternatively, for example, the detector unit 14a may determine the energy value of the annihilation gamma ray by integrally calculating the intensity of the analog signal output from the photodetector. Or, for example, the detector unit 14a may determine the energy value of the annihilation gamma ray by measuring the time (ToT: Time Over Threshold) during which the intensity of the analog signal output from the photodetector exceeds a preset threshold, and performing a nonlinear correction using the measured time.

[0025] Furthermore, for example, the detector unit 14a identifies the time when scintillation light is detected by the photodetector as the detection time of the annihilation gamma ray. Here, the detection time may be an absolute time or the elapsed time from the start of imaging.

[0026] The console device 20 receives various operations from the operator to the PET device 100 and controls the operation of the PET device 100 based on the received operations. Specifically, the console device 20 has an input interface 21, a display 22, a memory 23, and a processing circuit 24. Here, each part of the console device 20 is connected via a bus. Although this example illustrates the case where the rigging device 10 and the console device 20 are separate units, the console device 20 or a part of the components of the console device 20 may be included in the rigging device 10.

[0027] The input interface 21 receives various input operations from the operator, converts the received input operations into electrical signals, and outputs them to the processing circuit 24. For example, the input interface 21 receives operation inputs from the operator for setting imaging conditions and regions of interest (ROI).

[0028] The input interface 21 can, for example, be a mouse, keyboard, trackball, switch, button, joystick, non-contact input circuit using an optical sensor, audio input circuit, touchpad, or touch panel display, as appropriate.

[0029] In this embodiment, the input interface 21 is not limited to those equipped with these physical operating components. For example, an electrical signal processing circuit that receives an electrical signal corresponding to an input operation from an external input device provided separately from the device and outputs this electrical signal to the processing circuit 24 is also included as an example of the input interface 21. Furthermore, the input interface 21 may be provided on the mounting device 10. In addition, the input interface 21 may consist of a tablet terminal or the like that can communicate wirelessly with the main body of the console device 20. Here, the input interface 21 is an example of an input unit.

[0030] The display 22 displays various types of information. For example, the display 22 outputs medical images (PET images) generated by the processing circuit 24, and a GUI (Graphical User Interface) for receiving various operations from the operator. Various types of displays can be used as the display 22 as appropriate. For example, a liquid crystal display (LCD), a cathode ray tube (CRT) display, an organic electroluminescent display (OELD), or a plasma display can be used as the display 22.

[0031] The display 22 may be installed anywhere in the control room. Alternatively, the display 22 may be installed on the mounting device 10. Furthermore, the display 22 may be a desktop type, or it may consist of a tablet terminal or the like that can communicate wirelessly with the main body of the console device 20. Also, one or more projectors may be used as the display 22. Here, the display 22 is just one example of a display unit.

[0032] Memory 23 stores various data and programs used in the PET device 100. Memory 41 is implemented using semiconductor memory elements such as ROM (Read Only Memory), RAM (Random Access Memory), flash memory, hard disk, optical disc, etc. The storage area of ​​memory 23 may be located within the PET device 100 or in an external storage device connected via a network. Here, memory 23 is an example of a storage unit.

[0033] The processing circuit 24 controls the overall operation of the PET apparatus 100. The processing circuit 24 has a processor and memory such as ROM or RAM as hardware resources. The processing circuit 24 executes various functions such as control function 24a, synchronization information generation function 24b, and image reconstruction function 24c using a processor that executes a program loaded into memory. Here, processing circuit 44 is an example of a processing unit.

[0034] In the control function 24a, the processing circuit 24 controls the entire PET apparatus 100 by controlling each part of the pedestrian stand 10 and the console 20. For example, the processing circuit 24 controls the patient bed drive mechanism 13 to move the tabletop 11. Also, for example, the processing circuit 24 controls the PET detector 14 to collect count information of annihilation gamma rays emitted from the subject P and stores the collected count information in the memory 23.

[0035] In the simultaneous counting information generation function 24b, the processing circuit 24 generates simultaneous counting information using the counting information collected by the counting information collection circuit 15. Specifically, the processing circuit 24 refers to the counting information stored in the memory 23 and identifies sets of counting information that counted annihilation gamma rays approximately simultaneously based on the detection time of each set of counting information. The processing circuit 24 then generates simultaneous counting information associated with the identified sets of counting information and stores the generated simultaneous counting information in the memory 23. In addition, the processing circuit 24 corrects the time information difference between a reference detector unit 14a and other detector units 14a based on multiple time information acquired by multiple detector units 14a.

[0036] In the image reconstruction function 24c, the processing circuit 24 reconstructs the PET image based on the coincidence count information generated by the coincidence count information generation function 24b. Specifically, the processing circuit 24 reads the coincidence count information stored in the memory 23 and reconstructs the PET image by performing back projection processing using the read coincidence count information as projection data. The processing circuit 24 also stores the reconstructed PET image in the memory 23.

[0037] Furthermore, each function 24a to 24c is not limited to being implemented in a single processing circuit. A processing circuit 24 may be constructed by combining multiple independent processors, with each processor executing its respective program to realize each function 24a to 24c. Here, each function 24a to 24c may be implemented by being appropriately distributed or integrated across one or more processing circuits.

[0038] Although the console device 20 has been described as performing multiple functions on a single console, it is also acceptable for multiple functions to be performed by separate consoles. For example, the functions of processing circuits 24, such as the simultaneous counting information generation function 24b and the image reconstruction function 24c, may be distributed among multiple consoles.

[0039] Furthermore, part or all of the processing circuit 24 may not be included in the console device 20, but may also be included in an integrated server that performs processing on data acquired by multiple medical imaging diagnostic devices in a unified manner.

[0040] Furthermore, at least one of the processes—the generation of simultaneous counting information and the reconstruction of PET images—may be performed on either the console device 20 or an external workstation. Alternatively, both the console device 20 and the workstation may perform the processing simultaneously. As a workstation, a computer with hardware resources such as a processor that implements the functions corresponding to each process, and memory such as ROM or RAM, can be used as appropriate.

[0041] The configuration example of the PET apparatus 100 according to this embodiment has been described above. With this configuration, as described above, the PET apparatus 100 identifies a set of counting information in which annihilation gamma rays were counted approximately simultaneously from the counting information of annihilation gamma rays detected by a plurality of detector units 14a, and generates a PET image based on the simultaneous counting information associated with the identified set of counting information.

[0042] In such a PET apparatus 100, the analog signal processing in the PET detector 14 is affected by temperature. Temperature changes in the PET detector 14 can reduce the detection timing and energy resolution. Therefore, it is important to place the PET detector 14 in a stable temperature environment.

[0043] Photodetectors (photoelectric converters) such as SiPMs and A / D converters are known to be particularly susceptible to temperature changes. More specifically, the temperature influence in the PET detector 14 is predominantly due to the photoelectric converter. For this reason, it has been common practice to compensate for this by varying the applied voltage in response to temperature changes in the photoelectric converter to obtain stable energy information. Specifically, parameters were adjusted to enable appropriate voltage control based on measured temperatures of the photoelectric converter.

[0044] However, there was a risk that only the temperature of the A / D conversion element would change, such as when a rapid temperature change occurred inside the PET detector 14. In this case, a change in the temperature of the A / D conversion element would cause a problem in which the output values ​​of energy information and time information would change rapidly depending on the resolution of the A / D conversion element.

[0045] Therefore, the PET detector 14 in this embodiment is configured to output digital data that has been temperature-compensated based on the temperature of the A / D converter 145. Here, the PET detector 14 is an example of a radiation detector.

[0046] In addition to the temperature of the A / D converter 145, temperature compensation may also be performed based on the temperature of the photoelectric conversion element.

[0047] The configuration example of the PET detector 14 according to this embodiment will be described in more detail below. Figure 2 is a diagram showing an example of the configuration of the detector unit 14a according to this embodiment.

[0048] In the PET detector 14, each detector unit 14a includes an analog section 141, a DAS (Data Acquisition System), and a temperature sensor 147. For example, the DAS includes an oscillator 142, a PLL (Phase Locked Loop) 143, a distributor 144, an A / D converter 145, and an ASIC (Application Specific Integrated Circuit) 146.

[0049] In the PET detector 14, event data is collected for each block containing at least one detector unit 14a. In this embodiment, an example is given where event data is collected for each detector unit 14a.

[0050] The analog unit 141 outputs a pulse signal based on the incidence of radiation. Specifically, the analog unit 141 detects an analog signal based on the gamma ray detection result. Specifically, the analog unit 141 includes the aforementioned scintillator and photodetector (photoelectric conversion element), and converts the annihilation gamma rays emitted from positrons in the subject P into scintillation light, and converts the scintillation light into an analog pulse signal for output. Hereinafter, this pulse signal will be referred to as the detection signal. Here, the analog unit 141 is an example of a sensor unit.

[0051] Oscillator 142 generates a clock signal. For example, oscillator 142 is implemented by a circuit using a natural resonator such as a crystal oscillator.

[0052] The Phase Locked Loop (PLL) 143 converts the clock signal generated by the oscillator 142 into a clock signal of a predetermined frequency and outputs it.

[0053] The distributor 144 distributes the clock signal output from the PLL 143 to the A / D converter 145 and the ASIC 146.

[0054] The A / D converter 145 generates digital data by performing A / D conversion on the detection signal from the analog unit 141. The A / D converter 145 generates digital data (event data) for each event. Specifically, when the A / D converter 145 receives an input of an analog detection signal, it converts the detection signal into digital data. This digital data includes the detection location of the annihilation radiation (e.g., identification information of the detector unit 14a, photoelectric conversion element, scintillator, etc.), the energy value (e.g., the intensity of the detection signal, etc.), and the detection time (e.g., absolute time, elapsed time from the start of imaging, etc.). The A / D converter 145 generates time information by measuring the time when the intensity of the analog detection signal detected by the analog unit 141 exceeds a predetermined threshold, based on a clock signal generated by the oscillator 142, and converting this time into a digital signal. Here, the A / D converter 145 is an example of an A / D conversion unit.

[0055] The ASIC146 is configured to perform various functions, including a temperature acquisition function 146a, a time information generation function 146b, a counting information generation function 146c, and an output control function 146d.

[0056] In the temperature acquisition function 146a, the ASIC 146 acquires temperature information from the temperature sensor 147. Here, the ASIC 146 that implements the temperature acquisition function 146a is an example of an acquisition unit.

[0057] Here, for example, the temperature information is information indicating the temperature value of the A / D converter 145 or its vicinity measured by the temperature sensor 147. Alternatively, for example, the temperature information may also be information indicating the temperature category of the A / D converter 145 or its vicinity measured by the temperature sensor 147. The temperature category can be set, for example, in correspondence with the threshold values ​​described later.

[0058] In the time information generation function 146b, the ASIC 146 acquires time information (digital data) generated by the A / D converter 145 based on the synchronization signal generated by the synchronization signal generation unit. The ASIC 146 transmits the acquired time information to the console device 20.

[0059] Here, for example, the synchronization signal generator may be a scintillator included in the analog unit 141. In this case, the synchronization signal is a gamma ray generated by the self-destruction of the scintillator. For example, the ASIC 146 acquires time information when gamma rays are generated by the self-destruction of the scintillator. Alternatively, for example, the synchronization signal generator may be a gamma ray source placed in the opening of the mounting device 10. In this case, the synchronization signal may be a gamma ray emitted from the gamma ray source. Alternatively, for example, the synchronization signal generator may be the control function 24a of the console device 20. In this case, the synchronization signal may be a command transmitted from the control function 24a.

[0060] In the counting information generation function 146c, the ASIC 146 generates counting information (digital data) including the detection location, energy value, and detection time of annihilation gamma rays based on the analog detection signal output from the analog unit 141 and the time information generated by the A / D converter 145. The ASIC 146 transmits the generated counting information to the console device 20.

[0061] In the output control function 146d, the ASIC 146 performs output control to output compensated digital data based on temperature information acquired from the temperature sensor 147. Details of the output control based on temperature information will be described later. Here, the ASIC 146 that realizes the output control function 146d is an example of an output control unit.

[0062] While this explanation uses the ASIC146 as an example, it is not limited to this. For instance, other processing circuits implemented by processors such as a CPU (Central Processing Unit), GPU (Graphics Processing Unit), FPGA (Field Programmable Gate Array), SPLD (Simple Programmable Logic Device), or CPLD (Complex Programmable Logic Device) may be used instead of the ASIC146.

[0063] The temperature sensor 147 includes at least a sensor capable of measuring the temperature of the A / D converter 145. The temperature sensor 147 may be a sensor capable of measuring the temperature of the substrate on which the A / D converter 145 is mounted, as the temperature of the A / D converter 145. The temperature sensor 147 may further include a sensor capable of measuring the temperature of the SiPM (photoelectric particle). For example, a thermistor is used as the temperature sensor 147, but other temperature-measuring sensors such as thermocouples or radiation thermometers may also be used.

[0064] Here, temperature compensation will be explained in more detail with reference to the drawings. Figures 3 to 5 are diagrams illustrating the temperature compensation according to each embodiment.

[0065] In the output control function 146d, the ASIC 146 performs output control by setting a threshold value for the pulse signal from the analog unit 141 based on temperature information. In this embodiment, the threshold value for the pulse signal from the analog unit 141 is a threshold value for measuring the energy of the pulse signal.

[0066] Figure 3 illustrates the analog waveform W of the detection signal from the A / D converter 145 in a standard temperature environment. When the temperature information indicates a standard temperature environment, the ASIC 146 performs output control in the output control function 146d, setting a threshold Th0 for the detection signal from the analog unit 141. Here, the threshold Th0 is predetermined according to the base voltage VB0 of the A / D converter 145. The following explanation assumes that energy information E0 is obtained by A / D conversion of the detection signal of the analog waveform W using the threshold Th0.

[0067] Figure 4 illustrates the analog waveform W of the detection signal from the A / D converter 145 when only the A / D converter 145's temperature rises. At this time, the base voltage of the A / D converter 145 is VB1, which is higher than voltage VB0 as the temperature rises. Therefore, the analog waveform W of the detection signal from the A / D converter 145 transitions to a higher value (upward in Figures 3 and 4) as shown in Figure 4, as the base voltage of the A / D converter 145 rises. Consequently, in A / D conversion using a threshold Th0 corresponding to a standard temperature environment, energy information E11 is generated that is higher than energy information E0.

[0068] Thus, because the output value of the energy information changes due to temperature changes in the A / D converter 145, in the output control based on temperature information according to this embodiment, the threshold value set for the analog detection signal in order to perform A / D conversion is changed according to the temperature information.

[0069] Specifically, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 performs output control in the output control function 146d to set a threshold Th1 for the detection signal from the analog unit 141. In other words, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 changes the threshold set for the analog detection signal for A / D conversion from a threshold Th0 corresponding to the standard temperature environment to a threshold Th1 corresponding to the high-temperature environment. Here, the threshold Th1 is a value predetermined according to the base voltage VB1 of the A / D converter 145 or its range, and is higher than the threshold Th0.

[0070] When A / D conversion is performed using a threshold Th1 that is compatible with high-temperature environments, energy information E12 is generated that is lower than energy information E11. Therefore, it is possible to suppress the increase in the output value of energy information caused by the temperature rise in the A / D converter 145.

[0071] Figure 5 illustrates the analog waveform W when only the A / D converter 145 experiences a temperature decrease. At this time, the base voltage of the A / D converter 145 is VB2, which is lower than voltage VB0 as the temperature decreases. Therefore, the analog waveform W of the detection signal from the A / D converter 145 transitions to a lower value (downward in Figures 3 and 5) as shown in Figure 5, as the base voltage of the A / D converter 145 decreases. Consequently, in A / D conversion using a threshold Th0 corresponding to a standard temperature environment, energy information E21 is generated that is lower than energy information E0.

[0072] Therefore, in the output control based on temperature information according to this embodiment, when the temperature information indicates an environment with a lower temperature than the standard temperature environment, the ASIC 146 performs output control in the output control function 146d to set a threshold Th2 for the detection signal from the analog unit 141. In other words, when the temperature information indicates an environment with a lower temperature than the standard temperature environment, the ASIC 146 changes the threshold set for the analog detection signal in order to perform A / D conversion from a threshold Th0 corresponding to the standard temperature environment to a threshold Th2 corresponding to the low temperature environment. Here, the threshold Th2 is a value predetermined according to the base voltage VB2 of the A / D converter 145 or its range, and is lower than the threshold Th0.

[0073] When A / D conversion is performed using a threshold Th2 that is compatible with low-temperature environments, energy information E22 is generated that is higher than energy information E21. Therefore, it is possible to suppress the decrease in the output value of energy information caused by the temperature drop that occurs in the A / D converter 145.

[0074] Here, the flow of output control based on temperature information according to the embodiment will be described in more detail with reference to the drawings.

[0075] Figure 6 is a flowchart showing an example of the output control process flow according to the embodiment.

[0076] First, in the temperature acquisition function 146a, the ASIC 146 acquires temperature information from the A / D converter 145 via the temperature sensor 147 (S101).

[0077] Then, in the output control function 146d, the ASIC 146 sets a threshold value for the pulse signal from the analog unit 141 based on the temperature information, as described above with reference to Figures 3 to 5 (S102).

[0078] Note that processes S101 and S102 do not necessarily have to be performed every time. Also, if there is no change in temperature information, the same threshold will be set, so the threshold setting can be omitted.

[0079] In the time information generation function 146b, the ASIC 146 acquires time information generated by the A / D converter 145, which has a threshold set based on the temperature information. In the counting information generation function 146c, the ASIC 146 generates counting information based on the said time information (S103).

[0080] Subsequently, in the output control function 146d, the ASIC 146 outputs temperature-compensated digital data based on the generated time information and counting information, i.e., the temperature information of the A / D converter 145, to the console device 20 (S104).

[0081] Thus, the temperature compensation according to this embodiment is achieved by changing the threshold value set for the analog detection signal in order to perform A / D conversion according to the temperature. Specifically, in the output control function 146d, the ASIC 146 sets a threshold value for the pulse signal from the analog unit 141 based on the temperature information. In other words, the ASIC 146 suppresses changes in the output value from the A / D converter 145 due to temperature changes and controls the output so that digital data compensated based on the temperature information is output from the PET detector 14.

[0082] This makes it possible to minimize fluctuations in energy information even if there are significant temperature increases or decreases in the A / D converter 145 due to rapid temperature changes caused by the outside air or high count rate processing.

[0083] (Second embodiment) In the first embodiment, an example was described in which a threshold for measuring the energy of the pulse signal from the analog unit 141 is set based on temperature information, but the embodiment is not limited to this. In the output control function 146d, the ASIC 146 may set a threshold for the timing of the pulse signal from the analog unit 141 based on temperature information.

[0084] Here, the threshold for pulse signal timing is the threshold for the intensity of the detection signal from the analog unit 141, which the A / D converter 145 uses when generating time information.

[0085] Even with this configuration, the ASIC146 can suppress changes in the output value from the A / D converter 145 due to temperature changes.

[0086] The technology according to this embodiment can be appropriately combined with the technology according to the first embodiment. Specifically, the ASIC 146 may be configured to set thresholds for energy measurement of the pulse signal from the analog unit 141 and thresholds for generation of time information from the pulse signal, based on temperature information.

[0087] (Third embodiment) In the embodiments described above, output control is exemplified by setting a threshold for the pulse signal from the analog unit 141 to output temperature-compensated digital data, but the invention is not limited to this. In the output control function 146d, the ASIC 146 may output temperature-compensated digital data by controlling the operation of the analog unit 141 based on temperature information.

[0088] In the output control function 146d, the ASIC 146 determines the voltage to be applied to the SiPM (photoelectric conversion element) of the analog unit 141 based on temperature information. For example, a table or relational expression showing the relationship between temperature information and applied voltage is predetermined.

[0089] The table and related formulas may also show the correspondence between the temperature information of the A / D converter 145, the temperature information of the SiPM, and the applied voltage. In this case, the temperature sensor 147 further includes a sensor capable of measuring the temperature of the SiPM.

[0090] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 performs output control in the output control function 146d by applying a lower voltage to the SiPM than when the temperature information indicates an environment with a standard temperature environment. In other words, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 reduces the voltage applied to the SiPM, thereby causing the analog waveform W of the detection signal from the analog unit 141 to transition (for example, downwards in Figures 3 and 4).

[0091] For example, when the temperature information indicates an environment with a lower temperature than the standard temperature environment, the ASIC 146 performs output control in the output control function 146d by applying a higher voltage to the SiPM than when the temperature information indicates an environment with a standard temperature environment. In other words, when the temperature information indicates an environment with a lower temperature than the standard temperature environment, the ASIC 146 increases the voltage applied to the SiPM, thereby causing the analog waveform W of the detection signal from the analog unit 141 to transition (for example, upward in Figures 3 and 5).

[0092] Even with this configuration, the ASIC146 can suppress changes in the output value from the PET detector 14 due to temperature changes in the A / D converter 145.

[0093] The technology according to this embodiment can be appropriately combined with the technologies according to the above-described embodiments. For example, the ASIC 146 may be configured to set a threshold value for the pulse signal from the analog unit 141 and to determine the applied voltage to the SiPM based on temperature information.

[0094] (Fourth embodiment) In the output control function 146d of this embodiment, the ASIC 146 corrects the time information (digital data) generated by the time information generation function 146b based on temperature information. The ASIC 146 then outputs the temperature-compensated time information to the console device 20.

[0095] Even with this configuration, the ASIC 146 can suppress changes in digital data from the PET detector 14 due to temperature changes in the A / D converter 145. The technology according to this embodiment can be appropriately combined with the technologies according to the above-described embodiments.

[0096] (Fifth embodiment) In the output control function 146d of this embodiment, the ASIC 146 corrects the counting information (digital data) generated by the counting information generation function 146c based on temperature information. The ASIC 146 then outputs the temperature-compensated time information to the console device 20.

[0097] Even with this configuration, the ASIC 146 can suppress changes in digital data from the PET detector 14 due to temperature changes in the A / D converter 145. The technology according to this embodiment can be appropriately combined with the technologies according to the above-described embodiments.

[0098] (Sixth embodiment) In the output control function 146d according to this embodiment, the ASIC 146 outputs temperature information or a command instructing temperature compensation along with the generated digital data to the console device 20. The command instructing temperature compensation is generated based on the temperature information.

[0099] Furthermore, the console device 20 according to this embodiment corrects the digital data from the PET detector 14 based on temperature information from the PET detector 14 or a command instructing temperature compensation. Specifically, in the control function 24a, the processing circuit 24 controls the PET detector 14 to collect time information and coefficient information (digital data), applies temperature compensation to the collected digital data, and stores the temperature-compensated digital data in the memory 23. Here, the processing circuit 24 that realizes the control function 24a is an example of a control unit.

[0100] Even with this configuration, the PET apparatus 100 can suppress the influence of changes in digital data from the PET detector 14 due to temperature changes in the A / D converter 145. The technology according to this embodiment can be appropriately combined with the technologies according to the above-described embodiments.

[0101] (Seventh Embodiment) In the output control function 146d according to this embodiment, the ASIC 146 controls the temperature controller mounted on the A / D converter 145 based on temperature information.

[0102] The temperature controller is a heater, cooler, or combination thereof configured to adjust the temperature of the A / D converter 145. For example, a fan can be used as the cooler.

[0103] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 in the output control function 146d turns on the cooler.

[0104] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 in the output control function 146d rotates the fan at a higher speed than when the temperature information indicates a standard temperature environment.

[0105] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 in the output control function 146d turns off the heater.

[0106] For example, when the temperature information indicates an environment with a lower temperature than the standard temperature environment, the ASIC 146 in the output control function 146d turns off the cooler.

[0107] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 in the output control function 146d rotates the fan at a lower speed than when the temperature information indicates a standard temperature environment.

[0108] For example, when the temperature information indicates an environment with a higher temperature than the standard temperature environment, the ASIC 146 in the output control function 146d turns on the heater.

[0109] Even with these configurations, the ASIC146 can suppress changes in the output value from the PET detector 14 due to temperature changes in the A / D converter 145. The technology according to this embodiment can be appropriately combined with the technologies according to the above-described embodiments.

[0110] The temperature compensation method according to this embodiment may be implemented by a device independent of the PET device 100, such as a computer having a processor and memory as hardware resources. In this case, the processor mounted on the computer can implement the temperature compensation method according to this embodiment by executing a program read from ROM or the like and loaded into RAM.

[0111] Furthermore, the temperature compensation methods according to each embodiment may be implemented in a photon counting type X-ray computed tomography (PCCT) system. In this case, the processor mounted on the PCCT system can implement the temperature compensation methods according to each embodiment by executing a program read from ROM or the like and loaded into RAM.

[0112] For example, there are various types of X-ray CT scanners, such as third-generation CT and fourth-generation CT, but any type can be applied to each embodiment. Here, third-generation CT is a Rotate / Rotate-Type in which the X-ray tube and detector rotate together around the subject. Fourth-generation CT is a Stationary / Rotate-Type in which a large number of X-ray detection elements are fixed in a ring-shaped array, and only the X-ray tube rotates around the subject.

[0113] In the above description, the term "processor" refers to circuits such as CPUs, GPUs, ASICs, and Programmable Logic Devices (PLDs). PLDs include SPLDs, CPLDs, and FPGAs. A processor functions by reading and executing a program stored in a memory circuit. The memory circuit in which the program is stored is a computer-readable, non-temporary recording medium. Alternatively, instead of storing the program in a memory circuit, the processor may be configured to directly incorporate the program into its circuitry. In this case, the processor functions by reading and executing the program incorporated into the circuitry. Furthermore, instead of executing the program, the processor may implement the function corresponding to the program through a combination of logic circuits. In this embodiment, each processor is not limited to being configured as a single circuit; multiple independent circuits may be combined to form a single processor and implement its functions. Moreover, multiple components shown in Figure 1 or Figure 2 may be integrated into a single processor to implement its functions.

[0114] According to at least one embodiment described above, the effects of temperature changes in the radiation detector can be adequately compensated for.

[0115] While several embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. These novel embodiments can be carried out in a variety of other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims and their equivalents.

[0116] With respect to the above embodiments, the following additional notes are disclosed as aspects of the invention and selective features.

[0117] (Note 1) A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, An output control unit that outputs digital data compensated based on the temperature information. A radiation detector equipped with the following features.

[0118] (Note 2) A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, The output control unit that outputs the aforementioned digital data and A radiation detector having, A control unit that performs temperature compensation on the digital data from the radiation detector based on the temperature information. A nuclear medicine diagnostic device equipped with the following features.

[0119] (Note 3) The output control unit may set a threshold value for the pulse signal based on the temperature information.

[0120] (Note 4) The threshold may be a threshold related to the measurement of the energy of the pulse signal.

[0121] (Note 5) The threshold may be a threshold relating to the timing of the pulse signal.

[0122] (Note 6) The output control unit may correct the digital data based on the temperature information.

[0123] (Note 7) The aforementioned digital data may be at least one of time information and counting information.

[0124] (Note 8) The output control unit may determine the voltage applied to the sensor unit based on the temperature information.

[0125] (Note 9) The acquisition unit may further acquire temperature information from the sensor unit. The output control unit may determine the voltage applied to the sensor unit based on the temperature information of the sensor unit.

[0126] (Note 10) The radiation detector may further include a temperature controller for controlling the temperature of the A / D conversion unit. The output control unit may control the operation of the temperature controller based on the temperature information. [Explanation of Symbols]

[0127] 100 PET equipment 10. Mounting device 11 Top plate 12 berths 13 Bed drive mechanism 14 PET detector 14a Detector Unit 141 Analog section (sensor section) 142 Oscillators 143 PLL 144 Distributor 145 A / D converter (A / D conversion unit) 146 ASIC 146a Temperature acquisition function (acquisition part) 146b Time information generation function 146c Counting Information Generation Function 146d Output control function (output control unit) 147 Temperature sensor 20 Console device 21 Input Interfaces 22 displays 23 memory 24 Processing Circuits 24a Control function (control unit) 24b Coincidence information generation function 24c Image reconstruction function

Claims

1. A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, An output control unit that outputs digital data compensated based on the temperature information. Equipped with, The output control unit sets a threshold for the pulse signal based on the temperature information. Radiation detector.

2. The radiation detector according to claim 1, wherein the threshold is a threshold for measuring the energy of the pulse signal.

3. The radiation detector according to claim 1, wherein the threshold is a threshold relating to the timing of the pulse signal.

4. The radiation detector according to claim 1, wherein the output control unit corrects the digital data based on the temperature information.

5. The radiation detector according to claim 4, wherein the digital data is at least one of time information and counting information.

6. A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, An output control unit that outputs digital data compensated based on the temperature information. Equipped with, The output control unit determines the voltage applied to the sensor unit based on the temperature information. Radiation detector.

7. The acquisition unit further acquires temperature information from the sensor unit, The output control unit further determines the voltage applied to the sensor unit based on the temperature information of the sensor unit. The radiation detector according to claim 6.

8. The system further includes a temperature controller for controlling the temperature of the A / D conversion unit, The output control unit controls the operation of the temperature controller based on the temperature information. The radiation detector according to claim 1.

9. A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, The output control unit that outputs the aforementioned digital data and A radiation detector having, A control unit that performs temperature compensation on the digital data from the radiation detector based on the temperature information. Equipped with, The output control unit sets a threshold for the pulse signal based on the temperature information. Nuclear medicine diagnostic equipment.

10. A sensor unit that outputs a pulse signal based on the incidence of radiation, An A / D conversion unit that generates digital data by performing A / D conversion on the pulse signal, An acquisition unit that acquires temperature information from the A / D conversion unit, The output control unit that outputs the aforementioned digital data and A radiation detector having, A control unit that performs temperature compensation on the digital data from the radiation detector based on the temperature information. Equipped with, The output control unit determines the voltage applied to the sensor unit based on the temperature information. Nuclear medicine diagnostic equipment.

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