WO2016021493A1 - コンプトンカメラ用検出器及びコンプトンカメラ - Google Patents

コンプトンカメラ用検出器及びコンプトンカメラ Download PDF

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Publication number
WO2016021493A1
WO2016021493A1 PCT/JP2015/071779 JP2015071779W WO2016021493A1 WO 2016021493 A1 WO2016021493 A1 WO 2016021493A1 JP 2015071779 W JP2015071779 W JP 2015071779W WO 2016021493 A1 WO2016021493 A1 WO 2016021493A1
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Prior art keywords
radiation
layer
scattering layer
detector
scattering
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PCT/JP2015/071779
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English (en)
French (fr)
Japanese (ja)
Inventor
恵 玄蕃
能克 黒田
博 池淵
大介 松浦
忠幸 高橋
伸 渡辺
武田　伸一郎
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Mitsubishi Heavy Industries Ltd
Japan Aerospace Exploration Agency JAXA
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Mitsubishi Heavy Industries Ltd
Japan Aerospace Exploration Agency JAXA
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Application filed by Mitsubishi Heavy Industries Ltd, Japan Aerospace Exploration Agency JAXA filed Critical Mitsubishi Heavy Industries Ltd
Priority to US15/329,770 priority Critical patent/US10175368B2/en
Priority to EP15828957.9A priority patent/EP3163326B1/en
Publication of WO2016021493A1 publication Critical patent/WO2016021493A1/ja
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/29—Measurement performed on radiation beams, e.g. position or section of the beam; Measurement of spatial distribution of radiation
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01T—MEASUREMENT OF NUCLEAR OR X-RADIATION
    • G01T1/00—Measuring X-radiation, gamma radiation, corpuscular radiation, or cosmic radiation
    • G01T1/16—Measuring radiation intensity
    • G01T1/24—Measuring radiation intensity with semiconductor detectors
    • G01T1/242—Stacked detectors, e.g. for depth information

Definitions

  • the present invention relates to a Compton camera detector and a Compton camera.
  • Radiation detection devices are known which detect radiation emitted from a substance.
  • a gamma camera system is disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2013-33009).
  • This gamma camera system includes a gamma camera, distance measurement means, position calculation means, sensitivity correction information estimation means, resolution correction information estimation means, and image generation calculation means.
  • a gamma camera has a gamma ray detector and a collimator.
  • the distance measuring means can scan and measure the distance to the imaging target of the gamma camera.
  • the position calculation means calculates the positional relationship based on the distance between the gamma camera obtained by the scan measurement of the distance measurement means and the imaging target of the gamma camera.
  • the sensitivity correction information estimation means estimates the measurement sensitivity when measuring the imaging target with the gamma camera based on the positional relationship obtained from the position calculation means.
  • the resolution correction information estimation means estimates the resolution when measuring the imaging target with the gamma camera based on the positional relationship obtained from the position calculation means.
  • the image generation calculation means generates a gamma ray distribution image based on the measurement sensitivity estimated by the sensitivity correction information estimation means, the resolution estimated by the resolution correction information estimation means, and the gamma ray count data detected by the gamma camera. Do.
  • FIG. 1 is a schematic view showing this gamma camera system.
  • the gamma camera system 101a is a pinhole camera system. Therefore, the viewing angle of the detector 110a with respect to the radiation source 150 is defined by the aperture angle of the pinhole collimator 140 and is limited to 40 ° to 60 °. Therefore, in order to perform measurement in the entire circumferential (360 °) direction, for example, as shown in FIG. 2, the gamma camera system 101a is set on the rotation table 145, and the rotation table 145 is rotated several times ( If the viewing angle is 60 °, it is necessary to divide the measurement into six).
  • Non-Patent Document 1 http://www.hitachi-ce.co.jp/product/gamma_detector/ discloses such a system with a turntable.
  • a Compton camera is disclosed in Non-Patent Document 2 (http://www.jaxa.jp/press/2012/03/20120329_compton_1.pdf).
  • the Compton camera is a camera capable of measuring the incident direction of incident radiation (example: gamma ray) using Compton scattering.
  • the incident direction may be visualized using any display device.
  • FIG. 3A is a schematic view showing the operating principle of this Compton camera.
  • the Compton camera 101b simultaneously determines the energy E1 + E2 of the incident radiation R1 and the arrival direction ⁇ based on the measured position X1 and energy E1, and the position X2 and energy E2.
  • the position X1 and the energy E1 are the position X1 (x1, y1, z1) of the scattering when the radiation R1 is Compton scattered by the electrons in the scattering layer 110b1, and the energy E1 given to the electron by the radiation R1. It is. Also, the position X2 and the energy E2 are obtained by the absorbed position X2 (x2, y2, z2) and the absorbed energy E2 when the Compton scattered radiation R2 is photoelectrically absorbed in the absorption layer 110b2. is there. Then, based on the information, the position or type of the radiation source 150 is estimated. For example, as shown in FIG.
  • the incident radiation R1 is scattered by applying energy E1 at positions X1 in the plurality of scattering layers (Si) 110b1, and the scattered radiation R2 is in the positions in the plurality of absorbing layers (CdTe) 110b2. It is absorbed by applying energy E2 at X2.
  • the energy of the incident radiation and the arrival direction ⁇ are simultaneously determined. Then, based on the information, the position or type of the radiation source 150 is estimated.
  • This Compton camera 101b can detect radiation from the entire circumference (viewing angle 360 °; strictly speaking, solid angle 4 ⁇ steradian: 4 ⁇ [sr]) in principle.
  • this Compton camera 101b has a configuration in which the scattering layer 110b1 is disposed in front of the camera (in the incident direction) and the absorption layer 110b2 is disposed behind the scattering layer 110b1.
  • the detection efficiency of the hemisphere in front of the camera (view angle 180 °; strictly solid angle 2 ⁇ steradian) and the detection efficiency of the hemisphere behind the camera (view angle 180 °; strictly solid angle 2 ⁇ steradian) are compared
  • the detection efficiency of the hemisphere behind the camera becomes extremely small (example: about 1/10). Therefore, the practical viewing angle of the Compton camera 101b is 180 °, and practically only radiation from the hemispherical (2 ⁇ [sr]) direction can be detected. Therefore, in order to perform measurement in the entire circumference (viewing angle 360 °; 4 ⁇ [sr]), for example, as shown in FIG. 4, at least two measurements are also required for the Compton camera 101 b.
  • One object of the present invention is to provide a Compton camera detector and Compton camera that make it possible to reduce the number of measurement devices installed or to reduce the number of measurements by the measurement devices when measuring radiation. It is in.
  • a detector for a Compton camera includes a first radiation scattering layer, a second radiation scattering layer, and a radiation absorbing layer provided between the first radiation scattering layer and the second radiation scattering layer. Equipped with The first radiation scattering layer and the radiation absorbing layer constitute at least a part of the first detector, and the second radiation scattering layer and the radiation absorbing layer constitute at least a part of the second detector.
  • the Compton camera includes a Compton camera detector and an information processing apparatus.
  • the Compton camera detector has the above-described configuration.
  • the information processing apparatus responds to incident radiation to a signal output from the first radiation scattering layer and the radiation absorbing layer of the Compton camera detector or to a signal output from the second radiation scattering layer and the radiation absorbing layer Based on the position of the radiation source and the energy of the radiation are calculated.
  • the number of installed measurement devices when measuring radiation, can be reduced or the number of measurements by the measurement devices can be reduced.
  • FIG. 1 is a schematic view showing a gamma camera system of Patent Document 1.
  • FIG. 2 is a schematic diagram illustrating the operation of the gamma camera system of FIG.
  • FIG. 3A is a schematic view showing the operation principle of the Compton camera of Non-Patent Document 2.
  • FIG. 3B is a schematic view showing the configuration of the Compton camera of Non-Patent Document 2.
  • FIG. 4 is a schematic view showing the operation of the Compton camera of FIG. 3B.
  • FIG. 5 is a block diagram showing an exemplary configuration of a Compton camera according to some embodiments.
  • FIG. 1 is a schematic view showing a gamma camera system of Patent Document 1.
  • FIG. 2 is a schematic diagram illustrating the operation of the gamma camera system of FIG.
  • FIG. 3A is a schematic view showing the operation principle of the Compton camera of Non-Patent Document 2.
  • FIG. 3B is a schematic view showing the configuration of the Compton camera of Non-Patent Document
  • FIG. 6 is a schematic view showing a configuration example of a radiation detector according to some embodiments.
  • FIG. 7 is a plan view schematically showing a configuration example of a radiation detector module according to some embodiments.
  • FIG. 8 is a perspective view schematically showing a configuration example of a radiation detector in which modules according to some embodiments are stacked.
  • FIG. 9 is a schematic view showing the operation principle of the Compton camera according to some embodiments.
  • FIG. 10 is a flow diagram illustrating the operation of a Compton camera according to some embodiments.
  • FIG. 11A is a schematic view showing a modified example of the configuration of the radiation detector according to the embodiment.
  • FIG. 11B is a schematic view showing a modified example of the configuration of the radiation detector according to the embodiment.
  • FIG. 11C is a schematic view showing a modified example of the configuration of the radiation detector according to the embodiment.
  • FIG. 11D is a schematic view showing a modified example of the configuration of the radiation detector according to the embodiment.
  • FIG. 5 is a block diagram showing an exemplary configuration of a Compton camera according to some embodiments.
  • the Compton camera 5 includes a radiation detector 1 and an information processing device 2.
  • the radiation detector (detector for Compton camera) 1 is a detector of radiation used in the Compton camera 5. Incident radiation is detected, and a signal corresponding to the incident radiation is output to the information processing device 2. Details of the radiation detector 1 will be described later.
  • the information processing apparatus 2 calculates the position of the radiation source and the energy of the radiation based on the signal output from the radiation detector 1.
  • the information processing device 2 may be a computer operating with a program stored in a storage device, may be hardware (a dedicated data processing circuit), or may be a combination of both.
  • FIG. 6 is a schematic view showing a configuration example of a radiation detector 1 according to some embodiments.
  • the radiation detector 1 includes a first radiation scattering layer 11, a second radiation scattering layer 13, and a radiation absorbing layer 12.
  • the first radiation scattering layer 11 is a layer for Compton scattering of radiation (example: gamma ray).
  • the first radiation scattering layer 11 is provided on one side of the radiation absorbing layer 12 and may be a single layer or a plurality of layers may be stacked.
  • the first radiation scattering layer 11 mainly Compton scatters radiation from the hemisphere (solid angle 2 ⁇ [sr]) on one side with respect to the radiation absorption layer 12.
  • the first radiation scattering layer 11 is exemplified by a detector using a material having a high ability to scatter radiation, such as silicon (Si).
  • the first radiation scattering layer 11 is modularized layer by layer. In other words, the first radiation scattering layer 11 can detect the interaction with the gamma ray layer by layer.
  • the first radiation scattering layer 11 is given by the position X (x, y) in the layer of the scattering, the position (z) of the layer in the radiation detector 1, the scattering A value corresponding to the energy E (absorbed) can be output.
  • the second radiation scattering layer 13 has the same configuration and function as the first radiation scattering layer 11. However, the second radiation scattering layer 13 is provided on the other side of the radiation absorbing layer 12 (the side opposite to the first radiation scattering layer 11), and mainly on the other side of the radiation absorbing layer 12. Compton scatters radiation from (solid angle 2 ⁇ [sr]).
  • the radiation absorption layer 12 is a layer for photoelectrically absorbing the radiation that is Compton scattered by the first radiation scattering layer 11 and the second radiation scattering layer 13.
  • the radiation absorbing layer 12 is provided between the first radiation scattering layer 11 and the second radiation scattering layer 13 and may be a single layer or a plurality of layers may be stacked.
  • the radiation absorbing layer 12 is exemplified as a detector using a material having a high ability to absorb photons, such as cadmium tellurium (CdTe) or cadmium zinc tellurium (CdZnTe).
  • the radiation absorbing layer 12 is modularized layer by layer. In other words, the radiation absorbing layer 12 can detect the interaction with the gamma ray layer by layer.
  • the radiation absorbing layer 12 When an interaction with a gamma ray occurs, the radiation absorbing layer 12 is given by the position X (x, y) of the absorption in the layer, the position (z) of the layer in the radiation detector 1, the absorption A value corresponding to the energy absorbed (absorbed) can be output.
  • the layers of the first radiation scattering layer 11, the second radiation scattering layer 13, and the radiation absorbing layer 12 are disposed parallel to one another at a predetermined pitch interval.
  • the radiation detector 1 includes the first radiation scattering layer that Compton scatters radiation from one hemisphere (solid angle 2 ⁇ [sr]) with respect to the radiation absorption layer 12 11 and a second radiation scattering layer 13 for Compton scattering of radiation from the other side hemisphere (solid angle 2 ⁇ [sr]). Therefore, this radiation detector 1 can make the detection efficiency of the hemisphere on one side the same as the detection efficiency of the hemisphere on the other side. As a result, it is possible to detect the whole circumference (4 ⁇ [sr]) at one time by one Compton camera detector. Thereby, when measuring radiation, the number of installed measurement devices can be reduced, and the number of measurements by the measurement devices can be reduced.
  • the radiation absorbing layer 12 is shared by the first radiation scattering layer 11 and the second radiation scattering layer 13.
  • the radiation absorbing layer 12 includes the detector (first detector) including the first radiation scattering layer 11 and the radiation absorbing layer 12, and the second radiation scattering layer 13 and the radiation absorbing layer 12. Shared with other detectors (second detectors).
  • the number of layers (or thickness) can be relatively reduced by the amount of the radiation absorbing layer 12 of one detector.
  • solid angle 4 ⁇ [sr] solid angle 4 ⁇ [sr]
  • the number (or thickness) of the radiation absorbing layer 12 When the number (or thickness) of the radiation absorbing layer 12 is not relatively reduced, the number (or thickness) of the radiation absorbing layer 12 is relatively large. Therefore, the first radiation scattering layer 11 or the second radiation It becomes possible to reliably absorb the radiation scattered by the scattering layer 13.
  • the number of first radiation scattering layers 11 and the number of second radiation scattering layers 13 are as long as there are no special circumstances such as the radiation dose from one hemisphere and the radiation dose from the other hemisphere being significantly different.
  • the number of layers is preferably the same.
  • the detection efficiency of radiation from the hemisphere on the first radiation scattering layer 11 side can be made equal to the detection efficiency of radiation from the hemisphere on the second radiation scattering layer 13 side.
  • the first radiation scattering layer 11, the second radiation scattering layer 13, and the radiation absorbing layer 12 are preferably disposed sparsely with a small number of layers. If the number of layers is large and densely arranged, the signal due to scattering may increase and saturate. On the other hand, when the radiation dose is low, it is preferable to arrange the number of layers densely. If the number of layers is small and sparsely arranged, the detection efficiency is reduced.
  • the 1st radiation scattering layer 11, the 2nd radiation scattering layer 13, and the radiation absorption layer 12 are four layers, four layers, and two layers, respectively.
  • FIG. 7 is a plan view schematically showing a configuration example of the module.
  • the module 30 includes a sensor unit 31, a detection unit 32, and a tray 36.
  • the configuration of the module 30 is the same in any of the first radiation scattering layer 11, the second radiation scattering layer 13, and the radiation absorbing layer 12 except for the sensor unit 31.
  • the tray 36 holds the sensor unit 31 and the detection unit 32 at a predetermined position in the z direction in the radiation detector 1.
  • the tray 36 includes a first portion 36a and a plurality of second portions 36b (four in the example of FIG. 7).
  • the first portion 36 a is provided at the center of the tray 36 and has a shape on which the sensor unit 31 can be placed.
  • the plurality of second portions 36 b are provided at substantially equal intervals around the first portion 36 a and have a shape on which the detection unit 32 can be mounted.
  • the sensor unit 31 is mounted on the first portion 36a
  • the detection unit 32 is mounted on each of the plurality of second portions 36b.
  • the number of second portions 36 b increases or decreases depending on the number of detection units 32.
  • the sensor unit 31 and the plurality of detection units 32 are electrically connected.
  • the end 36 b 1 of the second portion 36 b is provided with an opening 33.
  • the opening 33 is penetrated by a support member 21 provided in each second portion 36 b and extending in the z direction from a pedestal (not shown).
  • the other end 36b2 of the second portion is inserted into the support member 22 provided in each second portion 36b and extending in the z direction from a pedestal (not shown).
  • the tray 36 holds the sensor unit 31 and the detection unit 32 at a predetermined position in the z direction by holding the second portions 36 b by the support members 21 and 22.
  • the sensor unit 31 Compton scatters or photoelectrically absorbs radiation (example: gamma radiation), and an electrical signal indicating the position in the xy plane where the radiation is scattered or absorbed, and the amount corresponding to the magnitude of the energy of the scattering or absorption Output
  • the sensor unit 31 includes a detection layer, a first surface electrode, and a second surface electrode (not shown).
  • the detection layers in the first radiation scattering layer 11 and the second radiation scattering layer 13 are layers for scattering radiation, and are exemplified as semiconductor layers.
  • the semiconductor layer is exemplified as a silicon (Si) layer.
  • the first surface electrode is a film formed in a lattice shape in the xy plane so as to cover one surface of the detection layer, and is exemplified by the conductive layer.
  • the conductor layer is exemplified by an aluminum (Al) layer.
  • the second surface electrode is a film formed on one side in the xy plane so as to cover the other side of the detection layer, and is exemplified by the conductive layer.
  • the semiconductor layer is a silicon (Si) layer
  • the conductor layer is exemplified by an aluminum (Al) layer.
  • the position of the scattering in the xy plane is detected as the position of the first surface electrode receiving the electrical signal by the scattering.
  • Ru an amount corresponding to the magnitude of the scattered energy is detected as the magnitude of the charge detected by the first surface electrode.
  • the detection layer in the radiation absorbing layer 12 is a layer for absorbing radiation, and is exemplified as a semiconductor layer.
  • the semiconductor layer is exemplified by a cadmium telluride (CdTe) layer and a cadmium zinc tellurium (CdZnTe) layer.
  • the first surface electrode is a film formed in a lattice shape in the xy plane so as to cover one surface of the detection layer, and is exemplified by the conductive layer.
  • the conductor layer is exemplified by platinum (Pt).
  • the second surface electrode is a film formed on one side in the xy plane so as to cover the other side of the radiation detection layer, and is exemplified by the conductive layer.
  • the conductor layer is exemplified by indium (In).
  • the position of absorption is detected as the position of the first surface electrode that has received the electrical signal by the absorption. Further, the amount corresponding to the energy imparted by absorption is detected as the magnitude of the charge detected by the first surface electrode.
  • the shapes of the electrodes of the first surface electrode and the second surface electrode are not symmetrical. However, even if radiation enters the sensor unit 31 from which side of the surface electrode, the radiation is not affected by the surface electrodes, and the scattering or absorption of radiation in the sensor unit 31 is not affected.
  • the shapes of the first surface electrode (in this example, grid shape) and the second surface electrode (in this example, all over) and the shape of the sensor unit 31 (in this example, square) are limited to those described above. Absent.
  • the sensor unit 31 may be another type of radiation detector.
  • a strip type detector is exemplified.
  • the sensor unit 31 includes a detection layer, a first surface electrode, and a second surface electrode (not shown).
  • the first surface electrode is a plurality of films formed in a strip shape extending in parallel to the x direction so as to cover one surface of the detection layer.
  • the first surface electrode is exemplified by aluminum (Al) when the detection layer is a cadmium telluride (CdTe) layer.
  • the second surface electrode is a plurality of films formed in a strip shape extending in parallel to the y direction so as to cover the other surface of the detection layer.
  • the second surface electrode is exemplified by platinum (Pt) when the detection layer is a cadmium telluride (CdTe) layer.
  • the detection unit 32 receives an electrical signal indicating the amount corresponding to the position and energy output from the sensor unit 31 from the wiring 34. Then, the detection signal corresponding to the electrical signal is output to the information processing device 2 through the wiring 35.
  • the sensor part 31 is divided into four area
  • FIG. 8 is a perspective view schematically showing a configuration example of a radiation detector in which the modules are stacked.
  • a plurality of modules 30 (a first radiation scattering layer 11, a radiation absorbing layer 12, and a second radiation scattering layer 13) are stacked in a housing 20.
  • seven layers of the second radiation scattering layer 13, six layers of the radiation absorbing layer 12, and seven layers of the first radiation scattering layer 11 are disposed in this order from the lower side in the z direction.
  • Each module 30 is fixed at a predetermined position in the housing 20 by the support members 21 and 22 extending in the z direction from the pedestal 23.
  • the modules 30 can be stacked closely by stacking the modules 30 continuously in the z direction without gaps.
  • the modules 30 can be stacked sparsely.
  • the modules 30 can be stacked closely.
  • the modules 30 can be sparsely stacked.
  • the position of the module 30 in the z direction can be specified as the position of the location where the module 30 is held by the support members 21, 22. Therefore, the position X of the Compton scattering or the photoelectric absorption is specified by the position (z) of the z coordinate by the place where the module 30 is held by the support members 21 and 22, and the first surface electrode of the sensor unit 31 of each module 30 It is specified by the position (x, y) of the x coordinate and the y coordinate at the inside position.
  • FIG. 9 is a schematic view showing the operation principle of the Compton camera according to some embodiments.
  • FIG. 10 is a flowchart showing the operation of the Compton camera according to some embodiments.
  • the radiation detector 1 measures, for example, radiation (example: gamma rays) from the radiation source 50a located in front (step S01). Specifically, radiation from the forward radiation source 50 a is incident on the radiation detector 1 and is first Compton scattered approximately in any one of the plurality of first radiation scattering layers 11 of the radiation detector 1. At this time, the first radiation scattering layer 11 (z1) where the scattering occurred is the change value of the charge corresponding to the position (x1, y1) where the scattering occurred in the sensor unit 31 and the energy E1 applied by the radiation. Output the signal shown.
  • radiation example: gamma rays
  • the detection unit 32 of the first radiation scattering layer 11 outputs a signal indicating the change value of the charge (corresponding to the energy E1) and the position X1 (x1, y1, z1) to the information processing device 2. Thereafter, the scattered radiation is photoelectrically absorbed in any one of the plurality of radiation absorbing layers 12 of the radiation detector 1. At this time, the radiation absorbing layer 12 (z2) where absorption has occurred is a signal indicating the position (x2, y2) where absorption has occurred in the sensor section 31 and the change value of the charge corresponding to the absorbed energy E2. Output.
  • the detection unit 32 of the radiation absorbing layer 12 outputs, to the information processing device 2, a signal indicating the change value of the charge (corresponding to the energy E2) and the position X2 (x2, y2, z2).
  • the scattering in the first radiation scattering layer 11 and the absorption in the radiation absorbing layer 12 occur almost simultaneously. Therefore, it is possible to judge that two events that occur almost simultaneously in time series are consecutive events due to one radiation. Accordingly, it can be distinguished from other scattering and absorption occurring in the first radiation scattering layer 11 and the radiation absorbing layer 12 and scattering and absorption occurring in the second radiation scattering layer 13 and the radiation absorbing layer 12.
  • the information processing device 2 converts the change value of the charge from the first radiation scattering layer 11 into energy E1, and converts the change value of the charge from the radiation absorption layer 12 into energy E2.
  • the energy E01 of the radiation source 50a is represented by the following formula (1).
  • E01 E1 + E2 (1)
  • the following equation (2) holds for the scattering angle ⁇ a .
  • E2 E01 / (1 + E01 (1-cos ⁇ a ) / mc 2 ) (2) Therefore, the following equation (3) is derived from the equation (1) and the equation (2).
  • the information processing device 2 performs the above-described steps S01 to S02 for a plurality of radiations from the radiation source 50a to obtain a plurality of scattering angles ⁇ a.
  • the code m means the mass of electrons
  • the code c means the speed of light.
  • the information processing apparatus 2 calculates the arrival direction of the radiation source 50a (step S03).
  • the scattering angle theta a to the position X1 and position X2 Prefecture, (direction of the radiation source 50a) the direction of incidence of the radiation is calculated with the following ranges. That is, the radiation source 50a is a position X1 and the vertex, and the height direction in the direction of the straight line connecting the position X1 and position X2, with a generatrix extending the scattering angle theta a from position X1 its height direction as a reference, It is on the side of cone 51a.
  • the radiation detector 1 measures, for example, radiation (example: gamma rays) from the radiation source 50b located behind (step S01). Specifically, radiation from the rear radiation source 50b is incident on the radiation detector 1, and is first Compton scattered approximately in any one of the plurality of second radiation scattering layers 13 of the radiation detector 1. At this time, the second radiation scattering layer 13 (z3) where the scattering occurred is the change value of the charge corresponding to the position (x3, y3) where the scattering occurred in the sensor unit 31 and the energy E3 given by the radiation.
  • radiation example: gamma rays
  • the detection unit 32 of the second radiation scattering layer 13 outputs a signal indicating the change value of the charge (corresponding to the energy E3) and the position X3 (x3, y3, z3) to the information processing device 2. Thereafter, the scattered radiation is photoelectrically absorbed in any one of the plurality of radiation absorbing layers 12 of the radiation detector 1. At this time, the radiation absorbing layer 12 (z4) where absorption has occurred is a signal indicating the position (x4, y4) where absorption has occurred in the sensor unit 31 and the change value of the charge corresponding to the absorbed energy E4. Output.
  • the detection unit 32 of the radiation absorbing layer 12 outputs, to the information processing device 2, a signal indicating the change value of the charge (corresponding to the energy E4) and the position X4 (x4, y4, z4).
  • the scattering in the second radiation scattering layer 13 and the absorption in the radiation absorbing layer 12 occur almost simultaneously. Therefore, it is possible to judge that two events that occur almost simultaneously in time series are consecutive events due to one radiation. Therefore, it is possible to distinguish the other scattering and absorption occurring in the second radiation scattering layer 13 and the radiation absorbing layer 12 and the scattering and absorption occurring in the first radiation scattering layer 11 and the radiation absorbing layer 12.
  • the energy E02 of the radiation source 50b is represented by the following equation (4).
  • E02 E3 + E4 (4)
  • the Compton scattering, the scattering angle theta b the following equation (5) holds.
  • E4 E02 / (1 + E02 (1-cos ⁇ b ) / mc 2 ) (5) Therefore, the following equation (6) is derived from the equation (4) and the equation (5).
  • cos ⁇ b 1 ⁇ mc 2 / E 4 + mc 2 / (E 3 + E 4) (6) That is, by substituting the E3, E4 in equation (6), the scattering angle theta b obtained. Then, the information processing apparatus 2, the plurality of radiation from the radiation source 50b, performs the steps S01 ⁇ S02, to obtain a plurality of scattering angles theta b.
  • the code m means the mass of electrons
  • the code c means the speed of light.
  • the information processing apparatus 2 calculates the arrival direction of the radiation source 50b (step S03).
  • the scattering angle theta b and the position X3 and the position X4 Prefecture, (direction of the radiation source 50b) incident direction of the radiation is calculated with the following ranges. That is, the radiation source 50b is the position X3 to the vertex, and the height direction in the direction of the straight line connecting the position X3 to the position X4, having a generatrix extending the scattering angle theta b from the position X3 its height direction as a reference, It is on the side of cone 51b.
  • the range of the incident direction corresponds to the side surface of the cone 51b.
  • a plurality of radiation emitted from the radiation source 50b by calculating a plurality of scattering angles theta b, respectively (steps S01 ⁇ S02), a plurality of cones to can be determined, respectively.
  • the direction corresponding to the overlapping position of the plurality of cones can be calculated as the direction of the final radiation source 50b.
  • the Compton camera according to some embodiments operates.
  • radiation from the forward radiation source 50a enters the radiation detector 1, mainly Compton scattered by one of the plurality of first radiation scattering layers 11, and a plurality of radiation absorptions when the photoelectric absorption in one layer 12, to calculate the scattering angle theta a and energy E01, you can identify the position of the radiation source 50a.
  • radiation from the rear radiation source 50 b enters the radiation detector 1 and is Compton scattered mainly by one of the plurality of second radiation scattering layers 13, and the radiation absorbing layer 12 If it is photoelectrically absorbed by one, to calculate the scattering angle theta b and energy E02, you can identify the position of the radiation source 50b.
  • the Compton camera 5 has a range of the solid angle 2 ⁇ [sr] of the second radiation scattering layer 13 side as well as the radiation source 50a in the range of the solid angle 2 ⁇ [sr] of the first radiation scattering layer 11 side.
  • the radiation source 50 b located inside can also be measured by the radiation detector 1. Therefore, a single Compton camera 5 can identify a radiation source within the range of solid angle 4 ⁇ [sr] at one time. Therefore, when measuring radiation, the number of installed measurement devices can be reduced, or the number of measurements by the measurement devices can be reduced.
  • the number and arrangement of the first radiation scattering layer 11, the second radiation scattering layer 13, and the radiation absorbing layer 12 in the radiation detector 1 are arbitrary. Some examples are shown below.
  • 11A to 11C are schematic views showing modifications of the configuration of the radiation detector 1 according to the embodiment.
  • the first radiation scattering layer 11a, the second radiation scattering layer 13a, and the radiation absorbing layer 12a are relatively densely stacked. In other words, the number of layers of each layer per unit thickness is relatively large.
  • the radiation detector 1a is characterized in that the probability that radiation is Compton scattered by the first radiation scattering layer 11a and the second radiation scattering layer 13a and photoelectrically absorbed by the radiation absorbing layer 12a is high (detection sensitivity is high). Therefore, it is suitable when the radiation dose to be measured is small.
  • the 1st radiation scattering layer 11, the 2nd radiation scattering layer 13, and the radiation absorption layer 12 are five layers, five layers, and three layers, respectively.
  • the first radiation scattering layer 11b, the second radiation scattering layer 13b, and the radiation absorbing layer 12b are stacked relatively sparsely. In other words, the number of layers of each layer per unit thickness is relatively small.
  • the radiation detector 1b is characterized in that the probability that radiation is Compton scattered by the first radiation scattering layer 11b or the second radiation scattering layer 13b and photoelectrically absorbed by the radiation absorbing layer 12b is low (detection sensitivity is low). Therefore, it is suitable when the radiation dose to be measured is high. In addition, the cost is low because the number of layers is small.
  • the 1st radiation scattering layer 11, the 2nd radiation scattering layer 13, and the radiation absorption layer 12 are three layers, three layers, and two layers, respectively.
  • the first radiation scattering layer 11c and the radiation absorbing layer 12c on the first radiation scattering layer 11c side are relatively densely stacked.
  • the second radiation scattering layer 13c and the radiation absorbing layer 12c on the second radiation scattering layer 13c side are stacked relatively sparsely. In other words, the number of layers in each unit thickness is relatively large on the first radiation scattering layer 11c side and relatively small on the second radiation scattering layer 13c side.
  • the radiation detector 1c has a high probability that the radiation is Compton scattered by the first radiation scattering layer 11c and photoelectrically absorbed by the radiation absorbing layer 12c, and the radiation is Compton scattered by the second radiation scattering layer 13c, and the radiation absorbing layer 12c It has a feature that the probability of photoelectric absorption is low. Therefore, it is suitable when the radiation dose to be measured is low on one side and high on the other side.
  • the 1st radiation scattering layer 11, the 2nd radiation scattering layer 13, and the radiation absorption layer 12 are five layers, three layers, and three layers, respectively.
  • the radiation scattering layer 11d and the radiation absorbing layer 12d are alternately laminated one by one, and the radiation is scattered to the outermost side (uppermost and lower sides in FIG. 11D) of the radiation detector 1d.
  • the layer 11d is disposed. Therefore, the radiation scattering layer 11d excluding the two outermost radiation scattering layers 11d (the uppermost radiation scattering layer 11d and the lowermost radiation scattering layer 11d) has the function and the second radiation scattering layer. It can be viewed as having the function of the radiation scattering layer.
  • the radiation scattering layer 11 d disposed between two adjacent radiation absorbing layers 12 can be said to be a radiation scattering layer in which the first radiation scattering layer and the second radiation scattering layer are integrated (identical).
  • a layer configured by arranging a radiation scattering layer 11d functioning as a first radiation scattering layer, a radiation absorbing layer 12d, and another radiation scattering layer 11d functioning as a second radiation scattering layer in this order can also be viewed that multiple sets of are arranged.
  • the radiation detector 1 d can also function in the same manner as the radiation detector 1 described above. Furthermore, since the arrangement range of the radiation absorbing layer 12 is expanded, the Compton scattered radiation can be more easily absorbed.
  • the radiation scattering layer 11d and the radiation absorbing layer 12d are alternately stacked one by one, but the radiation detector 1d is not limited to this example.
  • a plurality of radiation scattering layers 11d and a plurality of radiation absorbing layers 12d may be alternately stacked, or the number of radiation scattering layers 11d and the number of radiation absorbing layers 12d May be different.
  • the structure in which the radiation scattering layer 11d and the radiation absorbing layer 12d are alternately stacked, that is, the structure in which the absorbing layer is sandwiched in the middle of the scattering layer makes it easy to detect even the one having a large scattering angle among the Compton scattered gamma rays. This improves the effective area of the detector.
  • changing the detection sensitivity (detection efficiency) of the radiation detector 1 by increasing or decreasing the number of modules 30 of the first radiation scattering layer 11, the second radiation scattering layer 13, and the radiation absorbing layer 12 This can be realized by increasing or decreasing the distance between the modules 30.
  • the radiation detector according to some embodiments can freely change the detection sensitivity according to the radiation dose to be measured as described above.
  • Such a radiation detector 1 can be used, for example, in radiation measurement, X-ray measurement, gamma ray measurement, material analysis, security, resource exploration.

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  • General Physics & Mathematics (AREA)
  • High Energy & Nuclear Physics (AREA)
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  • Spectroscopy & Molecular Physics (AREA)
  • Measurement Of Radiation (AREA)
PCT/JP2015/071779 2014-08-04 2015-07-31 コンプトンカメラ用検出器及びコンプトンカメラ Ceased WO2016021493A1 (ja)

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EP3163326B1 (en) 2024-04-24
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JP2016035437A (ja) 2016-03-17

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