Signal processing device, signal processing method, signal processing program, and positron emission tomographic device

Abstract

To achieve a signal processing device capable of efficiently correcting detection timing in a light receiving element.SOLUTION: A signal processing device calculates a centroid position of fluorescence intensity detected by each of a plurality of detection units, specifies a detection unit on which radiation is incident and an energy window to which the radiation belongs based on the calculated centroid position, and corrects time at which the radiation is incident on the detection unit based on the specified detection unit and energy window.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a signal processing device, a signal processing method, a signal processing program, and a positron emission tomography apparatus. [Background technology]

[0002] BACKGROUND ART Radiography devices (for example, PET devices) are known that measure radiation (for example, gamma rays) emitted from a measurement object (for example, a human body) to observe the state of the measurement object (see Patent Document 1).

[0003] A radiographic imaging device has a conversion element that converts radiation into light (fluorescence) and multiple light-receiving elements that detect the light converted by the conversion element. The location of radiation on the measurement object can be identified based on the difference in timing (TOF) between the detection of fluorescence by each of the multiple light-receiving elements. For this reason, it is important to identify the detection timing by each light-receiving element. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-56700 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the detection timing of the light receiving element is subject to errors due to, for example, time walk, time skew, etc. While it is conceivable to correct the detection timing for each detection signal of each light receiving element, this would require the use of dedicated hardware to perform correction for each error factor, which would result in complicated processing.

[0006] An object of one aspect of the present invention is to provide a signal processing device capable of efficiently correcting detection timing in a light receiving element. [Means for solving the problem]

[0007] In order to solve the above-described problems, a signal processing device according to one aspect of the present invention processes an output signal from a radiation detection device including a plurality of detection units arranged in a matrix, each detection unit being constituted by a scintillator and a light receiving element that detects fluorescence from the scintillator, and is equipped with a processor that executes a calculation process that calculates a position of the center of gravity of the fluorescence intensity detected by each of the plurality of detection units; an identification process that identifies the detection unit into which the radiation is incident and the energy window to which the radiation belongs, based on the position of the center of gravity calculated in the calculation process; and a correction process that corrects the time at which the radiation is incident on the detection unit, based on the detection unit identified in the identification process and the energy window identified in the identification process. [Effects of the Invention]

[0008] According to one aspect of the present invention, a signal processing device capable of efficiently correcting the detection timing of a light receiving element can be realized. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a diagram showing the configuration of a radiation imaging apparatus according to an embodiment of the present invention; [Figure 2] FIG. 2 is a diagram illustrating the configuration of a radiation detection device of a radiation imaging apparatus. [Figure 3] FIG. 10 is a flowchart showing the processing flow in the signal processing method. [Figure 4] FIG. 1 is a diagram illustrating a time walk. [Figure 5] 10A and 10B are diagrams illustrating an example of a radiation detection result in an area corresponding to a detection unit. [Figure 6] FIG. 6 is an enlarged view of a region of FIG. 5. [Figure 7] FIG. 1 is a diagram showing the energy spectrum of gamma rays. [Figure 8] FIG. 10 is a diagram illustrating a detection map. [Figure 9]FIG. 10 is a diagram illustrating an example of the arrangement of the radiation detection device during calibration. [Figure 10] FIG. 10 is a diagram showing the relationship between element numbers, ROI numbers, and correction coefficients. [Figure 11] FIG. 10 is a diagram illustrating a superimposed analog detection signal. [Figure 12] 10A and 10B are diagrams showing detection maps with different numbers of divisions in the area Aij. [Figure 13] FIG. 10 is a diagram illustrating a superimposed analog detection signal. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the present invention will be described in detail below with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of a radiographic apparatus 10 according to an embodiment of the present invention. The left-right direction, the up-down direction, and the front-to-back direction of the paper in Fig. 1 are set as the X direction, the Y direction, and the Z direction, respectively. Fig. 2 is a diagram showing the configuration of a radiation detection apparatus 20 of the radiographic apparatus 10. Fig. 2 is a diagram showing the radiation detection apparatus 20 as viewed from the Y positive direction in Fig. 1.

[0011] The radiation imaging apparatus 10 includes a radiation detection device 20 and a signal processing device 30. The radiation imaging apparatus 10 is, for example, a positron emission tomography (PET) apparatus that captures an image of a measurement target using radiation (for example, gamma rays).

[0012] The radiation detection device 20 includes a detection unit 40 and a detection circuit 50 .

[0013] The detection section 40 includes a plurality of detection units 40(i,j) arranged in a matrix, and each detection unit 40(i,j) detects radiation and outputs an analog detection signal Sa. Here, the detection section 40 includes m detection units 40(1,1) to 40(n,m) in the X direction and n detection units 40(1,1) to 40(n,m) in the Y direction (m and n are integers equal to or greater than 2, i is an integer equal to or greater than 1 and equal to or less than m, and j is an integer equal to or greater than 1 and equal to or less than n). Here, m and n are 8, and the detection section 40 has 8*8=64 detection units 40(i,j).

[0014] The detection unit 40(i,j) has a scintillator 41(i,j) and a light-receiving element 42(i,j). The scintillator 41(i,j) is optically connected to the light-receiving element 42(i,j) in a one-to-one relationship. Specifically, the bottom surface of the scintillator 41(i,j) is optically connected to the light-receiving surface of the light-receiving element 42(i,j). As a result, the fluorescence generated in the scintillator 41(i,j) reaches the light-receiving element 42(i,j), which outputs a detection signal. In other words, the radiation incident on the scintillator 41(i,j) is detected.

[0015] Scintillator 41(i,j) is a conversion element (e.g., crystal) that converts radiation (e.g., gamma rays) into light (fluorescence). m scintillators 41(i,j) are arranged in the X direction and n scintillators 41(i,j) are arranged in the Y direction to form scintillator array 41. Note that reflective material 43 may be arranged between scintillators 41(i,j).

[0016] In this embodiment, Fast-LGSO (Ce:LuxGd(2-x)SiO5) is used for the scintillator 41(i,j). Other scintillator materials include LYSO (Lutetium Yttrium Orthosilicate), GAGG (Gd3(Ga,Al)5O12(Ce)), and LFS (Lutetium Fine Silicate).

[0017] The light receiving element 42(i, j) is Scintillator 41 The fluorescence emitted from (i,j) Light reception After that, amplification and outputs an analog detection signal Sa. Light receiving elements 42(i,j) are arranged in m pieces in the X direction and n pieces in the Y direction to form a light receiving element array 42. The analog detection signal Sa is output from the detection section 40 as a signal indicating that the detection unit 40(i,j) has detected radiation.

[0018] In this embodiment, an MPPC (Multi Pixel photon counter), which is a type of SiPM (Silicon Photo Multiplier), is used as the light receiving element 42(i,j), but other SiPMs can also be used.

[0019] The detection circuit 50 performs AD conversion on the analog detection signal Sa output from the light receiving element 42(i,j) to output a digital detection signal Sb. The digital detection signal Sb includes an element identifier IDe, a fluorescent light intensity I, and a detection time Td (a timestamp value). The element identifier IDe is information that identifies the light-receiving element 42(i,j) that detected the fluorescence, i.e., the detection unit 40(i,j) that detected the radiation. The element identifier IDe is, for example, the element number k assigned to the light-receiving element 42(i,j). The element number k can be defined as, for example, "k=i+(j-1)*n".

[0020] The fluorescence intensity I is the intensity of the fluorescence detected by the light receiving element 42(i, j). The detection time Td is the time when the light receiving element 42(i,j) detects the fluorescence, that is, a so-called time stamp value. As described above, the detection time Td includes errors due to time walk, time skew, and the like.

[0021] Here, the digital detection signal Sb is generated by processing the analog detection signal Sa for each light receiving element 42(i,j) in units of one event, i.e., a time width (for example, on the order of ps) corresponding to the incidence of one radiation ray, in order to process a larger number of events on the radiation detection device 20.

[0022] The signal processing device 30 is a device that processes the digital detection signal Sb output from the detection circuit 50, and includes a processor 31, a primary memory 32, a secondary memory 33, an input / output interface 34, and a bus 35. The processor 31, the primary memory 32, the secondary memory 33, and the input / output interface 34 are connected to each other via the bus 35.

[0023] A signal processing program P1, a detection map M0 (described later), and a correction coefficient R(k, p) are stored (non-volatilely) in the secondary memory 33. The processor 31 loads the signal processing program P1 stored in the secondary memory 33 onto the primary memory 32. Then, the processor 31 executes each step included in a signal processing method S1 (described later) in accordance with instructions included in the signal processing program P1 loaded onto the primary memory 32.

[0024] An example of a device that can be used as the processor 31 is a CPU (Central Processing Unit). An example of a device that can be used as the primary memory 32 is a semiconductor RAM (Random Access Memory). An example of a device that can be used as the secondary memory 33 is an HDD (Hard Disk Drive).

[0025] An input device and / or an output device are connected to the input / output interface 34. An example of an input device connected to the input / output interface 34 is a keyboard. An example of an output device connected to the input / output interface 34 is a display. The display is used, for example, to output the signal processing results described below.

[0026] Examples of interfaces that can be used as the input / output interface 34 include a PCI (Peripheral Component Interconnect) interface and a USB (Universal Serial Bus).

[0027] The signal processing program P1 may be recorded on a computer-readable, non-transitory, tangible recording medium. This recording medium may be the secondary memory 33 or another recording medium. For example, a tape, a disk, a card, a semiconductor memory, a programmable logic circuit, or the like may be used as the other recording medium.

[0028] (Flow of signal processing method) The flow of the signal processing method S1 performed by the signal processing device 30 will be described with reference to Fig. 3. Fig. 3 is a flow chart showing the flow of processing in the signal processing method S1.

[0029] The signal processing method S1 includes a calculation process S11, a specification process S12, and a correction process S13, and is used to process the digital detection signal output from the detection circuit 50. Sb is processed to correct the detection time.

[0030] Here, the digital detection signal Sb The error contained in the detection time Td of the signal is explained below. The error factors include time walk and time skew.

[0031] Time walk refers to an error in detection time due to the wave height of the analog detection signal Sa, i.e., the fluorescence intensity. Figure 4 is a diagram illustrating the time walk. It shows waveforms PW1 and PW2 of the analog detection signal Sa with different wave heights. The time at which the waveforms PW1 and PW2 reach a predetermined threshold Th is defined as the detection time Td. As shown in the figure, even if the peak times are the same, the waveform PW2 with a higher wave height reaches the threshold Th before the waveform PW1 with a lower wave height, resulting in a difference in detection time Td between the waveforms PW1 and PW2 equal to the time walk Tw. In other words, waveforms with lower energy tend to have a delayed detection time Td.

[0032] The time skew basically means an error in the detection time Td caused by a difference in the time it takes for the detection signal output from the light-receiving element 42(i,j) to reach the detection circuit 50. The time skew varies depending on, for example, the length of the wiring from the light-receiving element 42(i,j) to the detection circuit 50.

[0033] Errors in the detection time Td occur not only due to time walk and time skew, but also due to the individual characteristics of the detecting element and the light receiving element themselves. Therefore, it is reasonable to understand the error in the detection time Td as an error in the detection time Td that varies depending on the light receiving element 42(i,j), including the individual characteristics of the detecting element and the light receiving element themselves.

[0034] 5 is a diagram showing an example of the radiation detection results on an area A0 obtained by two-dimensionally projecting k inputs corresponding to the detection unit 40 through a centroid calculation. The area A0 is divided into areas Aij corresponding to the detection units 40(i, j). 6 is 6 is an enlarged view of the area Aij in FIG. 5. FIG.

[0035] The effects of gamma rays are classified into photoelectric absorption, which transfers all of the energy to the photodetector 42(i,j), and Compton scattering, which transfers only a portion of the energy. As shown in FIG. 5, photoelectric absorption is distributed locally for each scintillator in the region A0. Most of the Compton scattering is removed as noise by the energy window. However, Compton scattering also includes events (intracrystalline scattering ICS) that are detected by multiple photodetectors 42 and ultimately transfer all of the energy. This intracrystalline scattering ICS cannot be removed by the energy window of the radiation detection device 20. That is, as shown in FIG. 6, fluorescence generated in region Aij is generally scattered to adjacent regions Aij by intracrystalline scattering ICS. Therefore, for one event (incidence of one gamma ray), fluorescence from this gamma ray is received by multiple adjacent photodetectors 42. As a result, as will be described later, when a center of gravity calculation is performed within the range of one event (see equation (1) below), the center of gravity position (x, y) tends to deviate from the center of the area Aij.

[0036] As shown in Fig. 6, region Aij is divided into regions ROI1, ROI2, and ROI3 based on the center of region Aij. Region ROI2 is placed outside region ROI1, and region ROI3 is placed outside region ROI2. Here, region Aij is divided into three regions ROI1 to ROI3, but the number of divisions may be two, four, or more.

[0037] FIG. 7 is a diagram showing the energy spectrum of gamma rays. FIG. 7 shows the energy spectra SP1 to SPk of the light receiving elements 42 with element numbers 1 to k, respectively, and the energy spectrum SPT of the radiation detection device 20. Note that light receiving elements 42 that do not detect fluorescence do not output an energy spectrum SP. The energy spectrum SPT is obtained by adding the energy spectra SP1 to SPk. Here, the ranges of energy windows W1 to W3 are obtained by dividing the energy spectrum of each light receiving element 42. The energy windows W1, W2, and W3 have increasing energy in this order. The events acquired by the radiation detection device 20 are events within the energy window W4, and the energy window W4 also includes intra-crystalline scattering ICS.

[0038] Here, regions ROI1 to ROI3 shown in Fig. 6 correspond to energy windows W1 to W3 of the gamma ray energy spectrum shown in Fig. 7. That is, the center of gravity position (x, y) of high-energy gamma rays tends to be close to the center of region Aij, while the center of gravity position (x, y) of low-energy gamma rays tends to be far from the center of region Aij. Since the energy of gamma rays corresponds to the energy of fluorescence, regions ROI1 to ROI3 correspond to the energy of fluorescence and, further, to the time walk.

[0039] (1) Calculation process S11 The processor 31 calculates the centroid position (x, y) of the fluorescence intensity (radiation intensity) Iij detected by each of the multiple detection units 40(i, j). The centroid position (x, y) can be calculated by centroid calculation based on the following equation (1). Note that this calculation of the centroid position is performed within the range of one event, dividing the time period into sections. x=ΣinΣjm(i*Iij) / ΣinΣjm(Iij) y=ΣinΣjm(j*Iij) / ΣinΣjm(Iij) …Equation (1) Iij: Fluorescence intensity detected by detection unit 40(i,j)

[0040] (2) Specific processing S12 The processor 31 identifies the detection unit 40(i,j) into which the radiation is incident and the regions ROI1 to ROI3 based on the calculated center of gravity position (x,y). That is, the region Aij to which the center of gravity position (x,y) belongs and the regions ROI1 to ROI3 within the region Aij are identified.

[0041] The center of gravity position (x, y) can be represented on a detection map M0 having a plane corresponding to the detection section 40. FIG. 8 is a diagram showing the detection map M0. The detection map M0 is a two-dimensional surface obtained by dividing the plane on the detection section 40 into areas Aij corresponding to each of the detection units 40(i, j). The areas Aij are divided into areas R0I1 to R0I3. By representing the center of gravity position (x, y) on the detection map M0, it is possible to identify the area Aij, R0I1 to R0I3 to which the center of gravity position (x, y) belongs. As described above, the detection map M0 is stored in the secondary memory 33.

[0042] (3) Correction process S13 The processor 31 corrects the time (detection time Td) at which radiation enters the detection unit 40(i,j) based on the detection unit 40(i,j) and the regions ROI1 to ROI3 identified in the identification process.

[0043] The processor 31 corrects the detection time Td using the correction coefficient R corresponding to each of the plurality of detection units 40(i,j) and each of the regions ROI1 to ROI3.

[0044] Specifically, the detection time Td can be corrected based on the following equation (2). Td1(k,p)=Td0(k,p)+R(k,p)...Equation (2) Td0: Detection time Td before correction Td1: Corrected detection time Td R: Correction coefficient k: element number (k=(j-1)*m+i) p:ROI identifier(1:ROI1,2:ROI2,3:ROI3)

[0045] B. Calibration process Hereinafter, a calibration process for calibrating the correction coefficients corresponding to the radiation detection devices 20 will be explained using a simple system consisting of a pair of radiation detection devices 20. (1) Acquisition of calibration digital detection signals Sb1 and Sb2 The radiation detection device 20a acquires an output signal (digital detection signal Sb1) from the radiation detection device 20a and an output signal (digital detection signal Sb2) from another radiation detection device 20b arranged opposite to the radiation detection device 20a. The radiation detection device 20b has the same configuration as the radiation detection device 20a.

[0046] Radiation from the calibration radiation source SP (specifically, simultaneous measurement lines, described later) is detected by the radiation detection devices 20a and 20b to obtain calibration digital detection signals Sb1 and Sb2. FIG. 9 is a diagram showing an example of the arrangement of the radiation detection devices 20a and 20b during calibration. As shown in FIG. 8, multiple radiation detection devices 20 are arranged in a ring shape. Among them, the radiation detection devices 20a and 20b (detection units 40a and 40b) face each other with the calibration radiation source SP in between and detect radiation from the calibration radiation source SP. In this case, it is preferable that the radiation detection devices 20a and 20b are at approximately the same distance from the calibration radiation source SP. It is also preferable that the radiation detection devices 20a and 20b are approximately identical devices. Here, multiple radiation detection devices 20 are arranged in a ring shape, but other arrangements are also possible. For example, a pair of radiation detection devices 20a and 20b may be arranged opposite each other.

[0047] A pair of radiation rays (e.g., gamma rays) may be emitted simultaneously in opposite directions from the calibration radiation source SP. For example, a gamma ray source emits a pair of gamma rays in opposite directions due to the collision of an electron and a positron. This pair of radiation rays can be detected at virtually the same time by the detection units 40a and 40b, and is therefore called coincidence lines. Using this coincidence line enables calibration of the digital detection signal Sb.

[0048] The calibration source SP is a point source of 22Na, a gamma ray source, but it can also be a rotating source or a cylindrical source. Rotating sources and cylindrical sources can obtain data on a wider variety of simultaneous measurement lines than a point source.

[0049] Based on the output signals (digital detection signals Sb1, Sb2) from the radiation detection devices 20a, 20b, the correction coefficients R corresponding to each of the detection units 40(i,j) and each of the energy windows W1 to W3 are calibrated. Specifically, (2) calculation of the center of gravity, (3) classification of the center of gravity position (x,y), and (4) determination of the correction coefficients R are performed as follows.

[0050] (2) Center of gravity calculation The centroid position (x, y) of the fluorescence intensity (radiation intensity) Iij detected by each of the multiple detection units 40(i, j) is calculated. This calculation can be performed using equation (1), as in calculation process S11. Note that while calculation of the centroid position (x, y) for one event was sufficient in calculation process S11, here the centroid position (x, y) is calculated for each of multiple events. As a result, multiple centroid positions (x, y) are calculated.

[0051] (3) Classification of center of gravity position (x, y) The calculated center of gravity positions (x, y) are divided into the area Aij of the detection units 40a and 40b and the areas R0I1 to R0I3. A pair of simultaneous measurement lines has the same energy, and the center of gravity positions (x, y) are considered to be basically located in the same area R0I1 to R0I3 even if the area Aij is different.

[0052] (4) Identifying the correction coefficient R For each of the regions Aij and regions ROI1 to ROI3 classified as described above, a correction coefficient Rkl is determined based on the difference in detection time between the coincidence measurement lines. For example, if the peak centers of the detection time difference distribution (timing histogram) acquired by coincidence measurement are the region ROIp of element number k1 and the region ROIp of element number k2 of the detection unit 40a, the difference in detection time between these regions is considered to correspond to the difference in the correction coefficients R(k1,p) and R(k2,p) between them. The detection time difference distribution (timing histogram) is a histogram of the time differences calculated by coincidence counting. The individual correction coefficients R can be determined by statistically processing the results for various element numbers k (and regions ROIp) using multiple simultaneous measurement lines.

[0053] 10 is a diagram showing the correspondence relationship between element number k, ROI number p, and correction coefficient R. (a1) to (c1) show the timing histogram and correction coefficient Rkp for element number 12, 64, and ROI 1, (a2) to (c2) show the timing histogram and correction coefficient Rkp for element number 12, 64, and ROI 2, and (a3) ​​to (c3) show the timing histogram and correction coefficient Rkp for element number 12, 64, and ROI 3.

[0054] In this manner, in this embodiment, the area Aij corresponding to the detection unit 40(i, j) is divided into approximately concentric areas ROI1 to ROI3 corresponding to the energy window, and a correction coefficient is assigned to each divided area, thereby allowing the time walk and time skew to be corrected collectively.

[0055] FIG. 11 shows superimposed timing histograms. The timing histograms for regions ROI1 to ROI3 are superimposed. In (a), the timing histograms are superimposed without correcting the detection time Td, and in (b), the timing histograms are superimposed with the detection time Td corrected. Comparing (a) and (b) reveals that correcting the detection time Td reduces the width of the timing histogram, improving the time resolution.

[0056] FIG. 12 shows detection maps with different numbers of divisions of the region Aij. In (a), the region Aij is not divided, while in (b) to (d), the region Aij is divided into 2 to 4 divisions. FIG. 13 shows superimposed timing histograms. FIGS. 13(a) to (d) correspond to FIGS. 12(a) to (d). As shown, increasing the number of divisions of the region Aij improves the temporal resolution, and setting the number of divisions to 4 improves the temporal resolution by 53.2 ps compared to the case without divisions. Note that, as shown in FIG. 13, the degree of improvement in temporal resolution decreases as the number of divisions increases. In other words, there is a limit to the improvement in temporal resolution that can be achieved by increasing the number of divisions, due to a balance with statistical error.

[0057] The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of the present invention.

[0058] (summary)

[0059] The signal processing device of aspect 1 processes an output signal from a radiation detection device including a plurality of detection units arranged in a matrix, each detection unit being composed of a scintillator and a light-receiving element that detects fluorescence from the scintillator, and includes a processor that executes a calculation process that calculates the position of the center of gravity of the fluorescence intensity detected by each of the plurality of detection units, an identification process that identifies the detection unit into which the radiation is incident and the energy window to which the radiation belongs based on the position of the center of gravity calculated in the calculation process, and a correction process that corrects the time at which the radiation is incident on the detection unit based on the detection unit and the energy window identified in the identification process. This makes it possible to efficiently correct the time at which the radiation is incident based on the identified detection unit and energy window.

[0060] In a signal processing device of aspect 2, in the signal processing device of aspect 1, the center of gravity position is a position on a two-dimensional surface divided into regions corresponding to each of the plurality of detection units, each of the plurality of regions being divided into small regions corresponding to each of a plurality of energy windows, and in the identification process, the processor identifies a detection unit corresponding to an area among the plurality of regions that includes the center of gravity position as the detection unit onto which the radiation is incident, and identifies an energy window among the plurality of small regions that includes the center of gravity position as the energy window to which the radiation belongs, and in the correction process, the processor corrects the time using a correction coefficient corresponding to the detection unit identified in the identification process and the energy window identified in the identification process, among correction coefficients corresponding to each of the plurality of detection units and each of the plurality of energy windows. This makes it possible to efficiently correct the time of incidence of the radiation using the correction coefficients corresponding to the identified detection unit and energy window.

[0061] In the signal processing device of aspect 3, in the signal processing device of aspect 2, the processor further executes a calibration process to calibrate correction coefficients corresponding to each of the plurality of detection units and each of the plurality of energy windows based on an output signal from the radiation detection device and an output signal from another radiation detection device configured similarly to the radiation detection device and arranged opposite the radiation detection device, thereby making it possible to efficiently correct the time of radiation incidence using the correction coefficients corresponding to the identified detection unit and energy window.

[0062] The signal processing device of aspect 4 is the signal processing device of any one of aspects 1 to 3, wherein the radiation is gamma rays. This makes it possible to efficiently correct the time at which gamma rays are incident using a correction coefficient corresponding to the identified detection unit and energy window.

[0063] A signal processing method of aspect 5 is a signal processing method for processing an output signal from a radiation detection device including a plurality of detection units arranged in a matrix, each detection unit being composed of a scintillator and a light receiving element for detecting fluorescence from the scintillator, the method including: a calculation process by a processor calculating a position of the center of gravity of the fluorescence intensity detected by each of the plurality of detection units; an identification process by the processor identifying a detection unit into which radiation is incident and an energy window to which the radiation belongs, based on the position of the center of gravity calculated in the calculation process; and a correction process by the processor correcting the time at which the radiation is incident on the detection unit, based on the detection unit and the energy window identified in the identification process. This makes it possible to efficiently correct the time at which the radiation is incident, based on the identified detection unit and energy window.

[0064] The signal processing program of aspect 6 is a signal processing program for causing a computer to operate as the signal processing device of any one of aspects 1 to 4, and causes a processor included in the computer to execute the calculation process, the identification process, and the correction process, thereby enabling the time at which radiation is incident to be efficiently corrected using the computer.

[0065] A positron emission tomography apparatus according to aspect 7 includes the signal processing device according to any one of aspects 1 to 4 and the radiation detection device, thereby enabling efficient correction of the time at which gamma rays are incident in the positron emission tomography apparatus. [Explanation of symbols]

[0066] 10 Radiography equipment 20 Radiation detection equipment 30 Signal Processing Device 31 processors 32 Primary Memory 33 Secondary Memory 34 Input / Output Interface 35 Bus 40 Detector 40(i,j) detection units 41 Scintillator Array 41(i,j) Scintillator 42 Photodetector array 42(i,j) Photodetector 43 Reflective material 50 Detection circuit Sa Analog detection signal Sb Digital detection signal

Claims

1. A signal processing device that processes an output signal from a radiation detection device including a plurality of detection units arranged in a matrix, each detection unit being composed of a scintillator and a light receiving element that detects fluorescence from the scintillator, comprising: A calculation process for calculating a center position of the fluorescence intensity detected by each of the plurality of detection units; a process of identifying a detection unit into which the radiation is incident and an energy window to which the radiation belongs, based on the center of gravity position calculated in the calculation process; a correction process for correcting a time at which the radiation was incident on the detection unit based on the detection unit identified by the identification process and the energy window identified by the identification process, 23. A signal processing device comprising:

2. the center of gravity position is a position on a two-dimensional surface that is divided into regions corresponding to each of the plurality of detection units, each of the plurality of regions being divided into small regions corresponding to each of a plurality of energy windows; In the identification process, the processor identifies a detection unit corresponding to an area including the center of gravity among the plurality of areas as a detection unit into which the radiation is incident, and identifies an energy window corresponding to a small area including the center of gravity among the plurality of small areas as an energy window to which the radiation belongs; In the correction process, the processor corrects the time by using a correction coefficient corresponding to the detection unit identified in the identification process and the energy window identified in the identification process, among the correction coefficients corresponding to each of the plurality of detection units and each of the plurality of energy windows.

2. The signal processing device according to claim 1 .

3. the processor further executes a calibration process to calibrate correction coefficients corresponding to each of the plurality of detection units and each of the plurality of energy windows based on an output signal from the radiation detection device and an output signal from another radiation detection device that is configured similarly to the radiation detection device and is disposed opposite to the radiation detection device.

3. The signal processing device according to claim 2.

4. The radiation is gamma radiation.

4. The signal processing device according to claim 1, wherein the signal processing device is a digital signal processing device.

5. A signal processing method for processing an output signal from a radiation detection device including a plurality of detection units arranged in a matrix, each detection unit being composed of a scintillator and a light receiving element that detects fluorescence from the scintillator, comprising: A calculation process in which a processor calculates a center position of the fluorescence intensity detected by each of the plurality of detection units; a process of identifying a detection unit into which radiation is incident and an energy window to which the radiation belongs, based on the center of gravity position calculated by the calculation process, by the processor; a correction process in which the processor corrects the time when the radiation entered the detection unit based on the detection unit identified in the identification process and the energy window identified in the identification process.

23. A signal processing method comprising:

6. A signal processing program for causing a computer to operate as the signal processing device according to claim 1, the signal processing program causing a processor included in the computer to execute the calculation process, the determination process, and the correction process. A signal processing program comprising:

7. A signal processing device according to claim 4 and the radiation detection device. A positron emission tomography apparatus comprising:

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