Signal processing circuit, semiconductor pixel detector, information processing method, program, information processing device, information processing system, and device

Abstract

[Problem] To provide a signal processing circuit capable of specifying a change in signal strength due to a difference in the reaction position of radiation in the depth direction of a semiconductor with higher accuracy than in the prior art, and thereby more appropriately correcting a tail on a low energy side. Also, to provide a semiconductor pixel detector, an information processing method, a program, an information processing device, an information processing system, a device, and the like. [Solution] An embodiment of the present invention provides signal processing circuits that are respectively mounted on semiconductor pixels in a semiconductor pixel detector and that each process a signal generated in the semiconductor pixel. Each signal processing circuit comprises a first processing circuit and a second processing circuit. The first processing circuit has a first shaping circuit. The first shaping circuit shapes the signal such that the time constant of the first processing circuit is a first time constant and outputs a value of the shaped signal as a first signal value. The second processing circuit has a second shaping circuit. The second shaping circuit shapes the signal such that the time constant of the second processing circuit is a second time constant and outputs a value of the shaped signal as a second signal value.

Description

Signal processing circuit, semiconductor pixel detector, information processing method, program, information processing device, information processing system and device

[0001] The present invention relates to a signal processing circuit, a semiconductor pixel detector, an information processing method, a program, an information processing device, an information processing system, and an apparatus.

[0002] A circuit has been disclosed that divides a signal generated in a strip electrode connected to cadmium telluride (CdTe) or cadmium zinc telluride (CZT) into two paths for processing (see, for example, Non-Patent Document 1).

[0003] Natalia Auricchio et al. , "Twin shaping filter techniques to compensate the signals from CZT / CdTe detectors", IEEE Transactions on Nuclear Science, October 2005, vol. 52, no. 5, p. 1982-1988

[0004] Incidentally, when obtaining dynamic images of the brain or heart using single photon emission computed tomography (SPECT), a radioisotope is administered into the body, and the distribution of the radioisotope within the body is detected using a semiconductor detector.

[0005] In conventional SPECT using a scintillator such as NaI, it is difficult to separate images captured using multiple radioisotopes, making it necessary to use different types of radioisotopes with an interval between images. To solve this problem, SPECT using semiconductors such as CdTe and CZT has been proposed. However, in the case of SPECT using such semiconductors, the intensity of the generated signal varies depending on the position of radiation response in the depth direction of the semiconductor, resulting in the problem of a tail on the low-energy side.

[0006] In view of the above circumstances, the present invention provides a signal processing circuit, a semiconductor pixel detector, an information processing method, a program, an information processing device, an information processing system and device, etc., which are capable of more appropriately correcting the tail on the low-energy side by identifying with higher accuracy than conventional methods the change in signal intensity due to differences in the radiation reaction position in the depth direction of the semiconductor.

[0007] According to one aspect of the present invention, there is provided a signal processing circuit mounted on each semiconductor pixel in a semiconductor pixel detector and processing a signal generated in the semiconductor pixel. The signal processing circuit includes a first processing circuit and a second processing circuit. The first processing circuit has a first shaping circuit. The first shaping circuit shapes the signal so that the time constant of the first processing circuit is a first time constant, and outputs the value of the shaped signal as a first signal value. The second processing circuit has a second shaping circuit. The second shaping circuit shapes the signal so that the time constant of the second processing circuit is a second time constant, and outputs the value of the shaped signal as a second signal value.

[0008] According to this aspect, the change in signal intensity due to the difference in the reaction position of radiation in the depth direction in the semiconductor can be identified with higher accuracy than conventionally, thereby making it possible to more appropriately correct the tail on the low-energy side.

[0009] 1 is a configuration diagram showing an information processing system 100. FIG. 2 is a block diagram showing the hardware configuration of an information processing device 200. FIG. 3 is a side view showing the configuration of a SPECT device 300. FIG. 4 is a block diagram showing the configuration of a semiconductor pixel detector 400. FIG. 5 is a diagram showing the configuration of a signal processing circuit 600. FIG. 6 is a block diagram showing functions realized by the information processing device 200 (control unit 210). FIG. 7 is an activity diagram showing the flow of an information processing method executed by the information processing device 200. FIG. 8 is a diagram explaining a method of obtaining a predetermined function using gamma rays of a certain fixed energy. １３３ FIG. 10 is a diagram showing a spectrum when Ba is used.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings. Various features shown in the following embodiments can be combined with each other.

[0011] Incidentally, a program for realizing the software appearing in one embodiment may be provided as a non-transitory computer-readable recording medium, or may be provided so as to be downloadable from an external server, or may be provided so that the program is started on an external computer and its functions are realized on a client terminal (so-called cloud computing).

[0012] Furthermore, various information processing according to an embodiment may realize input and output corresponding to the input. Here, the form of information referenced in such information processing (hereinafter referred to as reference information) is not limited as long as an output is obtained as a result of the input. The reference information may be, for example, rule-based information such as a database, a lookup table, or a predetermined function (including a decision formula such as a regression formula constructed using a statistical method), a trained model that has previously trained the correlation between input and output, or a large-scale language model that can output a desired result by inputting a prompt.

[0013] In one embodiment, the term "unit" may include, for example, a combination of hardware resources implemented by a circuit in the broad sense and software information processing that can be specifically realized by these hardware resources. In one embodiment, various information is handled, and this information is represented, for example, by physical values ​​of signal values ​​representing voltage or current, high or low signal values ​​as a binary bit set consisting of 0 or 1, or quantum superposition (so-called quantum bits), and communication and calculations can be performed on the circuit in the broad sense.

[0014] Furthermore, a circuit in a broad sense is a circuit realized by at least an appropriate combination of a circuit, circuitry, a processor, a memory, etc. That is, it includes an application specific integrated circuit (ASIC), a programmable logic device (e.g., a simple programmable logic device (SPLD), a complex programmable logic device (CPLD), and a field programmable gate array (FPGA)), etc.

[0015] 1. Hardware Configuration In Section 1, the hardware configuration of this embodiment will be described.

[0016] 1-1. Information Processing System 100 FIG. 1 is a configuration diagram showing an information processing system 100. The information processing system 100 includes an information processing device 200, a SPECT device 300, and a semiconductor pixel detector 400, which are connected via a network. These components will be further described. Here, a system exemplified as the information processing system 100 is composed of one or more devices or components. Therefore, for example, even the information processing device 200 alone can be a system exemplified as the information processing system 100.

[0017] 2 is a block diagram showing the hardware configuration of the information processing device 200. The information processing device 200 is an information processing device connected to the semiconductor pixel detector 400. The information processing device 200 has a control unit 210, a storage unit 220, and a communication unit 250, and these components are electrically connected via a communication bus 260 inside the information processing device 200. Each component will be further described.

[0018] The control unit 210 processes and controls the overall operations related to the information processing device 200. The control unit 210 is, for example, a central processing unit (CPU) (not shown). The control unit 210 realizes various functions related to the information processing device 200 by reading out predetermined programs stored in the storage unit 220. In other words, information processing by software stored in the storage unit 220 is specifically realized by the control unit 210, which is an example of hardware, and can be executed as each functional unit included in the control unit 210. This will be described further in Section 2. Note that the control unit 210 is not limited to being a single unit, and multiple control units 210 may be provided for each function. A combination of these may also be used.

[0019] The storage unit 220 stores various information necessary for information processing of the information processing device 200. This may be implemented, for example, as a storage device such as a solid state drive (SSD) that stores various programs related to the information processing device 200 executed by the control unit 210, or as a memory such as a random access memory (RAM) that stores temporarily required information related to program calculations (arguments, arrays, etc.), or may be a combination of these.

[0020] The display unit 230 may be included in the housing of the information processing device 200 or may be externally attached. The display unit 230 displays a graphical user interface (GUI) screen that can be operated by a user. This is preferably implemented by selectively using display devices such as a CRT display, a liquid crystal display, an organic EL display, and a plasma display depending on the type of information processing device 200. In the following description, the display unit 230 is described as being included in the housing of the information processing device 200.

[0021] The input unit 240 may be included in the housing of the information processing device 200 or may be externally attached. For example, the input unit 240 may be implemented as a touch panel integrated with the display unit 230. A touch panel allows a user to input tapping, swiping, and the like. Of course, a switch button, a mouse, a QWERT keyboard, or the like may be used instead of a touch panel. That is, the input unit 240 accepts an operation input made by the user. The input is transferred as a command signal to the control unit 210 via the communication bus 260. The control unit 210 can then execute predetermined control and calculation as necessary.

[0022] The communication unit 250 is preferably a wired communication means such as USB, IEEE 1394, Thunderbolt (registered trademark), wired LAN network communication, etc., but may also include wireless LAN network communication, mobile communication such as 5G / LTE / 3G, Bluetooth (registered trademark) communication, etc. as necessary. In other words, it is more preferable to implement it as a collection of multiple communication means. In other words, the information processing device 200 communicates various information with the SPECT device 300 via the communication unit 250 over a network.

[0023] 3 is a side view showing the configuration of the SPECT device 300. The SPECT device 300 is a device that detects radiation (gamma rays) emitted from a radiopharmaceutical that has been administered to the subject 500 and selectively taken up by the living tissue of the subject 500, and collects signals that form the basis of projection data. In this embodiment, it is assumed that dynamic images of the heart of the subject 500 are obtained.

[0024] The SPECT device 300 includes a tabletop 310 and a bed 320. The tabletop 310 is a bed on which the subject 500 lies, and is placed on the bed 320. The bed 320 is controlled and moved by a bed driving circuit (not shown), and moves the subject 500 into the imaging opening of the SPECT device 300. A plurality of semiconductor pixel detectors 400 are arranged around the subject 500 moved into the imaging opening. The SPECT device 300 transmits signals detected by the semiconductor pixel detectors 400 to the information processing device 200.

[0025] 4 is a block diagram showing the configuration of the semiconductor pixel detector 400. The semiconductor pixel detector 400 includes a collimator 410, a plurality of semiconductor pixels 420, and a plurality of signal processing circuits 600. A signal processing circuit 600 is implemented for each semiconductor pixel 420. The signal processing circuit 600 will be described later.

[0026] The collimator 410 is disposed at the tip of the semiconductor pixel detector 400. The collimator 410 is disposed facing the subject 500 during imaging. The collimator 410 focuses gamma rays emitted from inside the body of the subject 500 into parallel rays and guides them to the semiconductor pixels 420.

[0027] The semiconductor pixel 420 is configured by arranging pixel electrodes on the surface of a cadmium telluride (CdTe) crystal. When a gamma ray photon (hereinafter simply referred to as "photon") guided by the collimator 410 is incident on and absorbed by the semiconductor pixel 420, electrons and holes are generated by photoelectric conversion. In other words, the photon is converted into an electric charge. The photon is then extracted as an electric charge generated inside the CdTe by a voltage applied to the pixel electrode and detected as a signal.

[0028] 5 is a diagram showing the configuration of the signal processing circuit 600. The signal processing circuit 600 is implemented for each semiconductor pixel 420 in the semiconductor pixel detector 400, and processes signals generated in the semiconductor pixels 420. The signal processing circuit 600 includes a CSA (Charge Sensitive Amplifier) ​​circuit 631, a leakage current compensation circuit 632, a first processing circuit 610, a second processing circuit 620, a comparison circuit 633, and an AD conversion circuit 634.

[0029] The CSA circuit 631 amplifies the signal detected by the semiconductor pixel 420 and outputs the amplified signal to the first processing circuit 610 and the second processing circuit 620. The leakage current compensation circuit 632 compensates for an increase in leakage current that occurs in an environment of gamma ray irradiation.

[0030] The first processing circuit 610 has a PZC circuit 611, a first shaping circuit 612, a first peak hold circuit 613, and a first sample hold circuit 614. Here, the first peak hold circuit 613 is an example of a "first peak storage circuit" in the claims. Also, the first sample hold circuit 614 is an example of a "first sample storage circuit" in the claims.

[0031] The PZC circuit 611 converts the signal input from the CSA circuit 631 into a signal having a tail with a desired time constant and outputs it. The first shaping circuit 612 shapes the signal output from the PZC circuit 611 so that the time constant of the first processing circuit 610 becomes a slow time constant (first time constant). The first shaping circuit 612 outputs the value of the shaped signal as a first signal value. The comparison circuit 633 compares the first signal value with a threshold and activates the first peak hold circuit 613 if the first signal value exceeds the threshold. The comparison circuit 633 activates the first sample hold circuits 614 in the signal processing circuits 600 implemented in the semiconductor pixels 420 surrounding the given semiconductor pixel 420 at the timing of activating the first peak hold circuit 613 in the signal processing circuit 600 implemented in the given semiconductor pixel 420. The first peak hold circuit 613 detects the peak value of the first signal value if the first signal value exceeds the threshold. The first peak hold circuit 613 stores and outputs the peak value as a first peak value. The first sample hold circuit 614 samples the first signal value at the timing when the peak value of the first signal value is detected or at any timing. The first sample hold circuit 614 stores and outputs the sampled first signal value as a first level value.

[0032] The second processing circuit 620 has a PZC circuit 621, a second shaping circuit 622, a second peak hold circuit 623, and a second sample hold circuit 624. Here, the second peak hold circuit 623 is an example of a "second peak storage circuit" in the claims. Also, the second sample hold circuit 624 is an example of a "second sample storage circuit" in the claims.

[0033] The PZC circuit 621 converts the signal input from the CSA circuit 631 into a signal with a tail of a desired time constant and outputs it. The second shaping circuit 622 shapes the signal output from the PZC circuit 621 so that the time constant of the second processing circuit 620 becomes the FAST time constant (second time constant). The second shaping circuit 622 outputs the value of the shaped signal as a second signal value. The comparison circuit 633 compares the second signal value with a threshold and activates the second peak hold circuit 623 if the second signal value exceeds the threshold. The comparison circuit 633 activates the second sample hold circuits 624 in the signal processing circuits 600 implemented in the semiconductor pixels 420 surrounding the given semiconductor pixel 420 at the timing of activating the second peak hold circuit 623 in the signal processing circuit 600 implemented in the given semiconductor pixel 420. If the second signal value exceeds the threshold, the second peak hold circuit 623 detects the peak value of the second signal value. The second peak hold circuit 623 stores and outputs the peak value as a second peak value. The second sample hold circuit 624 samples the second signal value at the timing when the peak value of the second signal value is detected or at any timing. The second sample hold circuit 624 stores and outputs the sampled second signal value as a second level value.

[0034] The AD conversion circuit 634 converts the analog signals output from the first processing circuit 610 and the second processing circuit 620 into digital data, and outputs the digital data to the information processing device 200 .

[0035] As described above, the signal processing circuit 600 includes two circuits (the first processing circuit 610 and the second processing circuit 620) with different time constants. The difference in the time constants of these two circuits produces an effect as a difference in the mobility of electrons and holes. This effect can be used to identify the reaction position of gamma-ray photons.

[0036] In other words, the signal processing circuit 600 can correct the tail on the low energy side, thereby identifying the change in signal intensity due to the difference in the reaction position of gamma ray photons in the depth direction of the CdTe crystal with higher accuracy than conventional methods.

[0037] 2. Functional Configuration The functional configuration of this embodiment will be described in Section 2. As described above, information processing by software stored in the storage unit 220 is specifically realized by the control unit 210, which is an example of hardware, and can be executed as each functional unit included in the control unit 210.

[0038] 6 is a block diagram showing functions realized by the information processing device 200 (control unit 210). As described above, the information processing device 200 includes the control unit 210. The control unit 210 is configured to execute each step of the information processing method described below. Specifically, the information processing device 200 (control unit 210) includes an acquisition unit 211, a calculation unit 212, and a generation unit 213.

[0039] The acquisition unit 211 is configured to acquire various information. The acquisition unit 211 is configured to execute an acquisition step. For example, the acquisition unit 211 acquires a first signal value shaped by the first shaping circuit 612 and a second signal value shaped by the second shaping circuit 622.

[0040] The calculation unit 212 is configured to calculate various information. The calculation unit 212 is configured to execute a calculation step. For example, the calculation unit 212 calculates correction information for correcting a change in signal intensity due to the reaction depth of the photon that generated the signal, based on the first signal value and the second signal value, and calculates the energy of the photon, based on at least one of the first signal value and the second signal value and the correction information.

[0041] The generating unit 213 is configured to generate various information. The generating unit 213 is configured to execute a generating step. For example, the generating unit 213 generates an image using the calculated correction information, and generates a spectrum using the calculated photon energy and the calculated correction information.

[0042] 3. Information Processing Method In Section 3, the flow of the information processing method of the information processing device 200 described above will be described. This information processing method is an information processing method for processing information output from the signal processing circuit 600. This information processing method includes an acquisition step, a calculation step, and a generation step. Details of each step will be described later.

[0043] 7 is an activity diagram showing the flow of an information processing method executed by information processing device 200. Below, an explanation will be given along with each activity in this activity diagram.

[0044] First, the control unit 210 in the information processing device 200 acquires a first peak value, which is the peak value of the first signal value shaped by the first shaping circuit 612, and a first level value, which is the first signal value sampled at an arbitrary timing (activity A110). That is, the first peak value is the peak value of a signal generated in a certain semiconductor pixel 420 and is output from the signal processing circuit 600 implemented in that certain semiconductor pixel 420. Furthermore, the first level values ​​are the values ​​of signals generated in multiple other semiconductor pixels 420 at the time the signal peak occurred and are output from the signal processing circuits 600 implemented in each of the multiple other semiconductor pixels 420. That is, the first level values ​​are detected in semiconductor pixels 420 surrounding the semiconductor pixel 420 where the first peak value was detected, at the same timing as the detection of the first peak value. The acquired multiple first level values ​​can be averaged and treated as common-mode noise. In other words, in the acquisition step, the first peak value and the first level value are acquired. In activity A110, for example, the following two-stage information processing is executed: (1) The communication unit 250 receives a first peak value output from a certain signal processing circuit 600 and first level values ​​output from the other plurality of signal processing circuits 600. (2) The control unit 210 stores in the storage unit 220 a first average value obtained by averaging the received first peak value and the plurality of first level values.

[0045] Next, the control unit 210 in the information processing device 200 acquires a second peak value, which is the peak value of the second signal value shaped by the second shaping circuit 622, and a second level value, which is the second signal value sampled at an arbitrary timing (activity A120). That is, the second peak value is the peak value of the signal generated in a certain semiconductor pixel 420 and is output from the signal processing circuit 600 implemented in that certain semiconductor pixel 420. The second level values ​​are the values ​​of the signals generated in multiple other semiconductor pixels 420 at the time the signal peak occurred and are output from the signal processing circuits 600 implemented in each of the multiple other semiconductor pixels 420. That is, the second level values ​​are detected in semiconductor pixels 420 surrounding the semiconductor pixel 420 where the second peak value was detected, at the same timing as the detection of the second peak value. The acquired multiple second level values ​​are averaged and can be treated as common-mode noise. In other words, in the acquisition step, the second peak value and the second level value are acquired. In activity A120, for example, the following two-stage information processing is performed: (1) The communication unit 250 receives a second peak value output from a certain signal processing circuit 600 and second level values ​​output from the other plurality of signal processing circuits 600. (2) The control unit 210 stores in the storage unit 220 a second average value obtained by averaging the received second peak value and the plurality of second level values.

[0046] Next, the control unit 210 in the information processing device 200 calculates a corrected first peak value (hereinafter also referred to as the "corrected first peak value") by subtracting the first average value as noise from the first peak value (activity A130). That is, the corrected first peak value is the first peak value before correction minus the common-mode noise. In other words, in the calculation step, the corrected first peak value is calculated based on the first peak value and the first level value. In activity A130, for example, the following three-stage information processing is performed: (1) The control unit 210 reads the first peak value and the first average value from the storage unit 220. (2) The control unit 210 performs a calculation process to calculate the corrected first peak value. (3) The control unit 210 stores the corrected first peak value in the storage unit 220.

[0047] Next, the control unit 210 in the information processing device 200 calculates a corrected second peak value (hereinafter also referred to as the "corrected second peak value") by subtracting the second average value as noise from the second peak value (activity A140). That is, the corrected second peak value is the second peak value before correction minus the common-mode noise. In other words, in the calculation step, the corrected second peak value is calculated based on the second peak value and the second level value. In activity A140, for example, the following three-stage information processing is performed: (1) The control unit 210 reads the second peak value and the second average value from the storage unit 220. (2) The control unit 210 performs a calculation process to calculate the corrected second peak value. (3) The control unit 210 stores the corrected second peak value in the storage unit 220.

[0048] Next, the control unit 210 in the information processing device 200 normalizes the corrected first peak value and the corrected second peak value and calculates their ratio. Next, the control unit 210 uses a predetermined function to calculate information regarding the photon reaction depth (hereinafter also referred to as "correction information") from the relationship between the ratio and the corrected first peak value or the corrected second peak value (activity A150). Here, the predetermined function is calculated in advance by inserting a relational expression calculated using radiation having a certain energy. The correction information is information that quantifies the photon reaction depth. In other words, in the calculation step, the correction information is calculated based on the corrected first peak value and the corrected second peak value, and further based on the corrected first peak value (first signal value) or the corrected second peak value (second signal value) and the predetermined function.

[0049] In activity A150, for example, the following five stages of information processing are performed. (1) The control unit 210 reads out the corrected first peak value and the corrected second peak value from the storage unit 220. (2) The control unit 210 performs a calculation process to calculate the ratio between them. (3) The control unit 210 reads out a predetermined function from the storage unit 220. (4) The control unit 210 performs a calculation process to calculate correction information. (5) The control unit 210 stores the correction information in the storage unit 220. By quantifying the correction information, it is possible to specifically calculate the energy of gamma-ray photons using information that quantifies the reaction position of gamma rays in the depth direction of the CdTe crystal. Activity A150 can provide a specific method for calculating the reaction position of gamma rays in the depth direction of the CdTe crystal.

[0050] FIG. 8 is a diagram illustrating a method for calculating a predetermined function using gamma rays of a certain energy. The vertical axis of FIG. 8 represents the second signal value (Kev), and the horizontal axis of FIG. 8 represents the ratio (second signal value / first signal value) of the first signal value (SLOW) to the second signal value (FAST). FIG. 8 shows that the intensity of the detected signal changes depending on the photon reaction depth. Therefore, a relational expression that corrects the signal intensity so that it is constant regardless of depth is obtained by fitting, and by interpolating or extrapolating this relational expression, a function (predetermined function) that determines the reaction depth of gamma rays of any energy can be obtained. Using this predetermined function, information (correction information) regarding the photon reaction depth can be calculated. According to this aspect, a specific method for calculating a function for identifying the reaction position of gamma rays in the depth direction of a CdTe crystal can be provided.

[0051] Next, the control unit 210 in the information processing device 200 calculates the photon energy by correcting the corrected first peak value or the corrected second peak value using the correction information (activity A160). In other words, in the calculation step, the photon energy is calculated based on at least one of the corrected first peak value and the corrected second peak value and the correction information. In activity A160, for example, the following three-stage information processing is performed: (1) The control unit 210 reads the corrected first peak value, the corrected second peak value, and the correction information from the storage unit 220. (2) The control unit 210 performs a calculation process to calculate the photon energy. (3) The control unit 210 stores the calculated photon energy in the storage unit 220.

[0052] Next, the control unit 210 in the information processing device 200 generates a spectrum using the calculated photon energy and correction information (activity A170). In other words, in the generation step, a spectrum is generated using the photon energy and correction information. In activity A170, for example, the following three stages of information processing are performed: (1) The control unit 210 reads out the calculated photon energy and correction information from the storage unit 220. (2) The control unit 210 performs a generation process to generate a spectrum. (3) The control unit 210 stores the generated spectrum in the storage unit 220.

[0053] FIG. 9 shows the radiation source １３３ 10 is a diagram showing a spectrum obtained when Ba is used. A spectrum obtained by directly using the detected signal as the photon energy (spectrum before correction) has a low-energy tail, whereas a spectrum obtained by using the photon energy calculated by the processing of this embodiment (spectrum after correction) does not have a low-energy tail.

[0054] Next, the control unit 210 in the information processing device 200 uses the correction information to define the reaction position of each photon and generate an image (activity A180). In other words, in the generation step, an image is generated using the correction information. In activity A180, for example, the following four stages of information processing are executed: (1) The input unit 240 accepts input of a window in the gamma ray spectrum data. (2) The control unit 210 applies the correction information to the spectrum corresponding to the input window and defines the reaction position of each photon. (3) The control unit 210 generates an image using the defined reaction position of each photon. (4) The control unit 210 stores the generated image in the memory unit 220.

[0055] The order in which the above activities are processed is not limited to the above, and the activities may be executed in any order as long as each process is executable.

[0056] According to the information processing method of this embodiment, when used for medical purposes, it is possible to more accurately identify changes in signal intensity due to differences in the radiation reaction position in the depth direction of a semiconductor, thereby more appropriately correcting the tail on the low-energy side. Furthermore, because of its simple configuration, the saved resources can be used for other core functions.

[0057] 4. Advantages of the Present Embodiment Over the Conventional Art In Section 4, the advantages of the present embodiment over the conventional art will be explained.

[0058] 4-1. Difficulties in imaging using multiple radioisotopes (RIs) (issues with conventional technology) In the case of cardiac SPECT in particular, it is necessary to acquire separate images from each RI. Separating images is difficult with methods using scintillators due to energy resolution limitations, and with semiconductor detectors such as CdTe and CZT, because charges cannot be fully collected within the detector, resulting in a low-energy tail. This is because the peaks of X-rays or gamma rays from multiple RIs overlap, making separation difficult.

[0059] 4-2. Signal Components Contaminate the Background (Issues with the Prior Art) In SPECT imaging using a single RI, it is necessary to subtract images created around peaks corresponding to background components such as scattering components within the body from an image created by selecting the central portion of the peak corresponding to the RI in the energy spectrum. When using semiconductor pixel detectors such as CdTe or CZT, if there is a low-energy tail when creating each image, signal components are mixed into the background image. Therefore, accurate subtraction is difficult when creating subtracted images.

[0060] 4-3. Accuracy of in vivo SPECT imaging (issues in the prior art) When performing SPECT imaging in vivo, it is important to accurately determine the reaction position of X-rays or gamma rays in the detector during the image reconstruction phase. However, with prior art, it was difficult to identify the depth position with high accuracy, and as a result, it was not possible to obtain a desirable sharp image.

[0061] 4-4. Advantages of the Present Embodiment In the present embodiment, by executing the information processing method described in Section 3, the problems of the prior art can be solved. Furthermore, the present embodiment is effective not only for cardiac SPECT, but also for pharmacokinetic observation, which distinguishes signals from different radioisotopes (RI) labeled on probe molecules corresponding to different targets and visualizes their distribution in the body. Furthermore, the present embodiment can function as a highly sensitive analytical device in non-destructive elemental analysis, since each peak seen in the spectrum does not have a low-energy tail. Therefore, the present embodiment is believed to have great industrial utility.

[0062] Although the embodiment of the present invention has been described above, the present invention is not limited to this and can be modified as appropriate within the scope of the technical idea of ​​the invention.

[0063] 5. Modifications In Section 5, modifications of this embodiment will be described.

[0064] An aspect of this embodiment may be a program configured to cause a computer to execute each step of the information processing method of this embodiment.

[0065] The control unit 210 performs writing (storing) and reading processes for various data and information in the memory unit 220, but this is not limited to this, and for example, the information processing for each activity may be performed using a register or cache memory within the control unit 210.

[0066] The semiconductor constituting the semiconductor pixel 420 is not limited to cadmium telluride (CdTe) and may be any of various semiconductors, such as silicon (Si), germanium (Ge), gallium arsenide (GaAs), indium phosphate (InP), cadmium zinc telluride (CZT), and diamond semiconductor.

[0067] The first processing circuit 610 of the signal processing circuit 600 does not have to include the first sample-and-hold circuit 614. The first processing circuit 610 does not have to include both the first peak-hold circuit 613 and the first sample-and-hold circuit 614. The first processing circuit 610 can achieve the effects of this embodiment by including at least the first shaping circuit 612.

[0068] The second processing circuit 620 of the signal processing circuit 600 does not have to include the second sample-and-hold circuit 624. The second processing circuit 620 does not have to include both the second peak-hold circuit 623 and the second sample-and-hold circuit 624. By including at least the second shaping circuit 622, the second processing circuit 620 can achieve the effects of this embodiment.

[0069] In the signal processing circuit 600, the first sample hold circuit 614 is arranged after the first peak hold circuit 613, but this is not limiting. For example, the first peak hold circuit 613 may be arranged after the first sample hold circuit 614, or the first peak hold circuit 613 and the first sample hold circuit 614 may be arranged in parallel. The same applies to the second peak hold circuit 623 and the second sample hold circuit 624.

[0070] In activity A110, the first peak value and the first level value are acquired, but this is not limiting. For example, the first peak value may be acquired without acquiring the first level value, or the first signal value may be acquired without acquiring both the first peak value and the first level value. In other words, the acquisition step may be an acquisition of the first signal value.

[0071] In activity A120, the second peak value and the second level value are acquired, but this is not limiting. For example, the second peak value may be acquired without acquiring the second level value, or the second signal value may be acquired without acquiring both the second peak value and the second level value. In other words, the acquisition step may be an acquisition of the second signal value.

[0072] In activity A150, the correction information is calculated by applying a predetermined function based on the ratio between the corrected first peak value and the corrected second peak value and the relationship between the corrected first peak value or the corrected second peak value, but this is not limited to this. The corrected first peak value may be replaced by the uncorrected first peak value, i.e., the first signal value. Furthermore, the corrected second peak value may be replaced by the uncorrected second peak value, i.e., the second signal value. Expressed in steps, the calculation step may calculate correction information for correcting a change in signal intensity due to the reaction depth of the photon that generated the signal, based on the first signal value and the second signal value.

[0073] In activity A150, the corrected first peak value and the corrected second peak value are normalized and the ratio between them is calculated, but this is not limiting. For example, the difference between the corrected first peak value and the corrected second peak value may be calculated, or the calculated difference may be divided by the corrected first peak value or the corrected second peak value.

[0074] The correction information is not limited to information that quantifies the reaction depth of photons, and does not have to be quantified as long as the correction information is in a form that corrects the detected signal to obtain photon energy.

[0075] In activity A160, the photon energy is calculated by correcting the corrected first peak value or the corrected second peak value using the correction information, but this is not limited to this. The corrected first peak value may be replaced by the uncorrected first peak value, i.e., the first signal value. Furthermore, the corrected second peak value may be replaced by the uncorrected second peak value, i.e., the second signal value. Expressed in steps, the calculation step may calculate the photon energy based on at least one of the first signal value and the second signal value and the correction information.

[0076] In the present embodiment, an example has been described in which the information processing method of the present embodiment is executed by the information processing device 200, but the present invention is not limited to this. For example, the method may be executed by a medical imaging device such as a SPECT device 300, by other medical devices, or by a non-medical device. In this case, the device includes a signal processing circuit 600 and a control unit, and the control unit is configured to process information output from the signal processing circuit 600. The device also includes a program of the present embodiment and a control unit, and the control unit is configured to execute the program.

[0077] 6. Others The present invention may be provided in the following forms.

[0078] (1) A signal processing circuit is implemented for each semiconductor pixel in a semiconductor pixel detector and processes a signal generated in the semiconductor pixel, the signal processing circuit comprising: a first processing circuit; and a second processing circuit, wherein the first processing circuit has a first shaping circuit that shapes the signal so that the time constant of the first processing circuit is a first time constant and outputs the value of the shaped signal as a first signal value, and the second processing circuit has a second shaping circuit that shapes the signal so that the time constant of the second processing circuit is a second time constant and outputs the value of the shaped signal as a second signal value.

[0079] According to this aspect, the tail on the low energy side is corrected, so that the change in signal intensity due to the difference in the reaction position of the radiation in the depth direction of the semiconductor can be identified with higher accuracy than before.

[0080] (2) In the signal processing circuit described in (1) above, the first processing circuit further has a first peak storage circuit, which, when the first signal value exceeds a threshold, detects the peak value of the first signal value and stores and outputs the peak value as a first peak value; and the second processing circuit further has a second peak storage circuit, which, when the second signal value exceeds a threshold, detects the peak value of the second signal value and stores and outputs the peak value as a second peak value.

[0081] According to this embodiment, it is possible to identify with higher accuracy the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor.

[0082] (3) In the signal processing circuit described in (2) above, the first processing circuit further has a first sample storage circuit, which samples the first signal value at an arbitrary timing and stores and outputs the sampled first signal value as a first level value, and the second processing circuit further has a second sample storage circuit, which samples the second signal value at an arbitrary timing and stores and outputs the sampled second signal value as a second level value.

[0083] According to this embodiment, it is possible to identify with even higher accuracy the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor.

[0084] (4) A semiconductor pixel detector comprising a plurality of semiconductor pixels and a signal processing circuit according to any one of (1) to (3) above, wherein the signal processing circuit is implemented for each of the semiconductor pixels.

[0085] According to this aspect, when used for medical purposes, it is possible to identify with higher accuracy than ever before changes in signal intensity due to differences in the radiation reaction position in the depth direction of the semiconductor.

[0086] (5) An information processing method for processing information output from a signal processing circuit described in any one of (1) to (3) above, comprising an acquisition step, a calculation step, and a generation step, wherein in the acquisition step, the first signal value and the second signal value are acquired, in the calculation step, correction information for correcting a change in intensity of the signal due to a reaction depth of the photon that generated the signal is calculated based on the first signal value and the second signal value, in the calculation step, the energy of the photon is calculated based on at least one of the first signal value and the second signal value and the correction information, in the generation step, a spectrum is generated using the energy of the photon and the correction information, and in the generation step, an image is generated using the correction information.

[0087] According to this aspect, when used in medical applications, the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor can be identified with higher accuracy than before, thereby making it possible to more appropriately correct the tail on the low-energy side. Furthermore, due to the simple configuration, the saved resources can be used for other core functions.

[0088] (6) In the information processing method described in (5) above, which processes information output from the signal processing circuit described in (2) or (3) above, the first signal value includes the first peak value and the second signal value includes the second peak value.

[0089] According to this embodiment, it is possible to identify with higher accuracy the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor.

[0090] (7) In the information processing method described in (6) above, which processes information output from the signal processing circuit described in (3) above, the first signal value further includes the first level value detected at the same timing as the detection of the first peak value in the semiconductor pixels surrounding the semiconductor pixel where the first peak value is detected, and the second signal value further includes the second level value detected at the same timing as the detection of the second peak value in the semiconductor pixels surrounding the semiconductor pixel where the second peak value is detected, and the calculation step calculates the corrected first peak value based on the first peak value and the first level value, calculates the corrected second peak value based on the second peak value and the second level value, calculates the correction information based on the corrected first peak value and the corrected second peak value, and calculates the energy of the photon based on the correction information and at least one of the corrected first peak value and the corrected second peak value in the calculation step.

[0091] According to this embodiment, it is possible to identify with even higher accuracy the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor.

[0092] (8) In the information processing method described in any one of (5) to (7) above, in the calculation step, the correction information is further calculated based on the first signal value or the second signal value and a predetermined function.

[0093] According to this aspect, it is possible to provide a specific method for calculating the radiation reaction position in the depth direction of the semiconductor.

[0094] (9) In the information processing method described above in (8), the predetermined function is calculated by inserting a relational expression calculated using radiation having a certain energy.

[0095] According to this aspect, it is possible to provide a specific method for calculating a function for identifying the radiation reaction position in the depth direction of a semiconductor.

[0096] (10) In the information processing method described in any one of (5) to (9) above, the correction information is information that quantifies the reaction depth.

[0097] According to this aspect, the photon energy can be specifically calculated using information that quantifies the radiation reaction position in the depth direction of the semiconductor.

[0098] (11) A program configured to cause a computer to execute each step of the information processing method described in (5) above.

[0099] According to this aspect, when used in medical applications, the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor can be identified with higher accuracy than before, thereby making it possible to more appropriately correct the tail on the low-energy side. Furthermore, due to the simple configuration, the saved resources can be used for other core functions.

[0100] (12) An information processing device connected to the semiconductor pixel detector described in (4) above, comprising a control unit, the control unit configured to execute each step of the information processing method described in (5) above.

[0101] According to this aspect, when used in medical applications, the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor can be identified with higher accuracy than before, thereby making it possible to more appropriately correct the tail on the low-energy side. Furthermore, due to the simple configuration, the saved resources can be used for other core functions.

[0102] (13) An information processing system comprising the semiconductor pixel detector according to (4) above and the information processing device according to (12) above.

[0103] According to this aspect, when used in medical applications, the change in signal intensity due to the difference in the radiation reaction position in the depth direction of the semiconductor can be identified with higher accuracy than before, thereby making it possible to more appropriately correct the tail on the low-energy side. Furthermore, due to the simple configuration, the saved resources can be used for other core functions.

[0104] (14) An apparatus comprising a signal processing circuit according to any one of (1) to (3) above and a control unit, wherein the control unit is configured to process information output from the signal processing circuit.

[0105] According to this aspect, it is possible to provide an apparatus that can more appropriately correct the tail on the low energy side.

[0106] (15) An apparatus comprising the program according to (11) above and a control unit, the control unit being configured to execute the program.

[0107] According to this aspect, it is possible to provide an apparatus that can more appropriately correct the tail on the low energy side.

[0108] (16) The device according to (14) or (15) above, wherein the device is an imaging device.

[0109] According to this aspect, it is possible to provide an imaging device that can more appropriately correct the tail on the low-energy side.

[0110] (17) The device according to any one of (14) to (16) above, wherein the device is a medical device.

[0111] According to this aspect, it is possible to provide a medical device that can more appropriately correct the tail on the low energy side. Of course, this is not a limitation.

[0112] 100: Information processing system 200: Information processing device 210: Control unit 211: Acquisition unit 212: Calculation unit 213: Generation unit 220: Storage unit 230: Display unit 240: Input unit 250: Communication unit 260: Communication bus 300: SPECT device 310: Top board 320: Bed 400: Semiconductor pixel detector 410: Collimator 420: Semiconductor pixel 500: Subject 600: Signal processing circuit 610: First processing circuit 611: PZC circuit 612: First shaping circuit 613: First peak hold circuit 614: First sample hold circuit 620: Second processing circuit 621: PZC circuit 622: Second shaping circuit 623 : Second peak hold circuit 624 : Second sample hold circuit 631 : CSA circuit 632 : Leakage current compensation circuit 633 : Comparison circuit 634 : AD conversion circuit

Claims

1. A signal processing circuit mounted for each semiconductor pixel in a semiconductor pixel detector, for processing a signal generated in the semiconductor pixel, comprising: a first processing circuit and a second processing circuit, wherein the first processing circuit has a first shaping circuit, which shapes the signal so that the time constant of the first processing circuit is a first time constant, and outputs the value of the shaped signal as a first signal value, and the second processing circuit has a second shaping circuit, which shapes the signal so that the time constant of the second processing circuit is a second time constant, and outputs the value of the shaped signal as a second signal value.

2. A signal processing circuit according to claim 1, wherein the first processing circuit further comprises a first peak storage circuit, which detects the peak value of the first signal value when the first signal value exceeds a threshold value, and stores and outputs the peak value as a first peak value; and the second processing circuit further comprises a second peak storage circuit, which detects the peak value of the second signal value when the second signal value exceeds a threshold value, and stores and outputs the peak value as a second peak value.

3. A signal processing circuit according to claim 2, wherein the first processing circuit further comprises a first sample storage circuit, which samples the first signal value at an arbitrary timing and stores and outputs the sampled first signal value as a first level value, and the second processing circuit further comprises a second sample storage circuit, which samples the second signal value at an arbitrary timing and stores and outputs the sampled second signal value as a second level value.

4. A semiconductor pixel detector comprising: a plurality of semiconductor pixels; and a signal processing circuit according to any one of claims 1 to 3, wherein the signal processing circuit is implemented for each of the semiconductor pixels.

5. An information processing method for processing information output from a signal processing circuit according to any one of claims 1 to 3, comprising an acquisition step, a calculation step, and a generation step, wherein in the acquisition step, the first signal value and the second signal value are acquired, in the calculation step, correction information is calculated based on the first signal value and the second signal value to correct changes in signal intensity due to the reaction depth of the photon that generated the signal, in the calculation step, the energy of the photon is calculated based on at least one of the first signal value and the second signal value and the correction information, in the generation step, a spectrum is generated using the photon energy and the correction information, and in the generation step, an image is generated using the correction information.

6. An information processing method according to claim 5, which processes information output from the signal processing circuit according to claim 2 or 3, wherein the first signal value includes the first peak value, and the second signal value includes the second peak value.

7. An information processing method according to claim 6, for processing information output from the signal processing circuit according to claim 3, wherein the first signal value further includes the first level value detected at the same timing as the detection of the first peak value in the semiconductor pixels surrounding the semiconductor pixel where the first peak value was detected, and the second signal value further includes the second level value detected at the same timing as the detection of the second peak value in the semiconductor pixels surrounding the semiconductor pixel where the second peak value was detected, and the calculation step calculates the corrected first peak value based on the first peak value and the first level value, calculates the corrected second peak value based on the second peak value and the second level value, calculates the correction information based on the corrected first peak value and the corrected second peak value, and calculates the energy of the photon based on the correction information and at least one of the corrected first peak value and the corrected second peak value.

8. An information processing method according to any one of claims 5 to 7, wherein the calculation step further calculates the correction information based on the first signal value or the second signal value and a predetermined function.

9. An information processing method according to claim 8, wherein the predetermined function is calculated by inserting a relational expression calculated using radiation having a certain energy.

10. An information processing method according to any one of claims 5 to 9, wherein the correction information is information that quantifies the reaction depth.

11. A program configured to cause a computer to execute each step of the information processing method according to claim 5.

12. An information processing device connected to the semiconductor pixel detector of claim 4, comprising a control unit, the control unit configured to execute each step of the information processing method of claim 5.

13. An information processing system comprising: a semiconductor pixel detector according to claim 4; and an information processing device according to claim 12.

14. An apparatus comprising: a signal processing circuit according to any one of claims 1 to 3; and a control unit, wherein the control unit is configured to process information output from the signal processing circuit.

15. An apparatus comprising: a program according to claim 11; and a control unit, wherein the control unit is configured to execute the program.

16. An apparatus according to claim 14 or 15, wherein the apparatus is an imaging apparatus.

17. A device according to any one of claims 14 to 16, wherein the device is a medical device.

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