Compton imaging system suitable for gamma ray detection in complex radiation field

Abstract

The invention discloses a Compton imaging system suitable for gamma ray detection in a complex radiation field, and solves the problem that an existing Compton camera cannot reconstruct an image or an imaging result is affected in a complex radiation environment, and the Compton imaging system specifically comprises a front-end detection unit, a front-end electronics control unit and a rear-end data processing and control unit, the front-end detection unit comprises a shielding shell, and a scattering layer array detection module and an absorption layer array detection module which are arranged in the shielding shell in parallel; the front-end electronics control unit comprises a signal processing module, a communication module and a control module; the signal processing module is respectively connected with the scattering layer array detection module and the absorption layer array detection module; the signal processing module is connected with the signal processing module and the rear-end data processing and control unit through the communication module; the control module is connected with the communication module. The imaging system provided by the invention can reduce the interference of gamma camera shooting outside the target view field on the front-end detection unit, and improves the imaging quality.

Description

TECHNICAL FIELD

[0001] The present application relates to a Compton imaging system, in particular to a Compton imaging system suitable for gamma ray detection in a complex radiation field. BACKGROUND

[0002] A Compton camera is a detection system for nuclide detection and gamma ray imaging, and its basic working principle is to use the principle of Compton scattering. Gamma rays undergo Compton scattering in the scatter layer detector, and the recoil electrons and scattered photons are detected by the scatter detector and the absorption detector, respectively. By measuring the energy and position information of the recoil electrons and scattered photons, combining the Compton scattering formula, and using the back projection reconstruction algorithm, a spatial gamma radioactivity distribution image is given.

[0003] A Compton camera generally has a double-layer structure, including a scatter layer and an absorption layer. In order to improve the imaging efficiency, a Compton camera sometimes also adopts a multi-layer structure. On the one hand, in Compton imaging, due to the close distance between the scatter layer and the absorption layer detectors, it is impossible to distinguish forward scattering events and backward scattering events in time. When the camera works in a radiation field with a complex gamma ray source distribution, it is impossible to better distinguish the gamma rays incident from the front and the back of the camera, and it is also impossible to determine whether it is a forward scattering event or a backward scattering event, which will result in the camera being unable to reconstruct the image. On the other hand, the rays incident from a certain angle on the side of the camera are likely to continuously act between the detection units (especially the scatter layer array unit), causing crosstalk, affecting the accurate judgment of the energy deposition position, and thus affecting the imaging result. Therefore, the Compton camera is only suitable for the case where the ray source distribution is within a certain angle in front of the Compton camera, which limits its environmental applicability. SUMMARY

[0004] In order to solve the technical problems that the existing Compton camera cannot better distinguish the gamma rays incident from the front and the back of the camera in a complex radiation environment, resulting in the inability to reconstruct the image, and the rays incident from the side are likely to continuously act between the detection units, causing crosstalk and affecting the imaging result, the present application provides a Compton imaging system suitable for gamma ray detection in a complex radiation field.

[0005] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0006] A Compton imaging system suitable for gamma ray detection in a complex radiation field, characterized in that it comprises a front-end detection unit, a front-end electronic control unit, and a back-end data processing and control unit.

[0007] The front-end detection unit comprises a shielding shell, and a scatter layer array detection module and an absorption layer array detection module arranged in parallel in the shielding shell.

[0008] The scattering layer array detection module and the absorption layer array detection module are used for receiving gamma rays and converting the gamma rays into corresponding detection information;

[0009] The front-end electronic control unit comprises a signal processing module, a communication module and a control module;

[0010] The input end of the signal processing module is connected with the output end of the scattering layer array detection module and the absorption layer array detection module respectively, the output end of the signal processing module is connected with the input end of the communication module, the output end of the communication module is connected with the input end of the signal processing module and the input end of the back-end data processing and control unit respectively, and the control module is connected with the communication module.

[0011] The signal processing module is used for receiving the detection information, extracting effective Compton events from the detection information, and sending the effective Compton events to the back-end data processing and control unit through the communication module under the control of the control module; and the communication module is used for information transmission between the signal processing module and the back-end data processing and control unit.

[0012] Further, the scattering layer array detection module comprises a scattering layer PCB board, N×N arrayed scattering detection elements on the scattering layer PCB board, a scattering layer positioning grid and a front shielding grid sleeved on the N×N scattering detection elements; N≥8; the scattering layer positioning grid is located between the scattering layer PCB board and the front shielding grid; the scattering layer PCB board is provided with a scattering layer flexible flat cable plug used for connecting with the front-end electronic control unit; the output end of the N×N scattering detection elements is connected with the corresponding terminal of the scattering layer flexible flat cable plug respectively.

[0013] The absorption layer array detection module comprises an absorption layer PCB board, M×M arrayed absorption detection elements on the absorption layer PCB board, and an absorption layer positioning grid sleeved on the M×M absorption detection elements; M>N; the absorption layer PCB board is provided with an absorption layer flexible flat cable plug used for connecting with the front-end electronic control unit; the output end of the M×M absorption detection elements is connected with the corresponding terminal of the absorption layer flexible flat cable plug respectively.

[0014] The N×N scattering detection elements and the M×M absorption detection elements are arranged in a staggered manner.

[0015] Further, the scattering detection element comprises a photoelectric device mounted on the scattering layer PCB board, a scintillator coupled to the photoelectric device through optical glue on the bottom surface, a reflective coating coated on the side surface and the top surface of the scintillator, and a protective shell sleeved outside the reflective coating.

[0016] The scintillator is a quadrangular prism structure, the cross section of the scintillator is a square, the side length of the square is a, and 2mm≤a≤4mm.

[0017] The thickness of the reflective coating is 0.08mm-0.12mm;

[0018] The structure of the absorption detection element is the same as that of the scattering detection element;

[0019] The height of the scintillator bottom surface to the top surface of the scattering detection element is L1, and 4mm≤L1≤7mm; the output end of the photoelectric device of the scattering detection element is connected with the corresponding terminal of the soft-wire plug (15) of the scattering layer;

[0020] The height of the scintillator bottom surface to the top surface of the absorption detection element is L2, and 8mm≤L2≤12mm; the output end of the photoelectric device of the absorption detection element is connected with the corresponding terminal of the soft-wire plug of the absorption layer.

[0021] Further, the a=3mm;

[0022] The scintillator is CsI, GAGG or LYSO.

[0023] Further, the protective shell is made of aluminum or Teflon material;

[0024] The thickness of the protective shell is h≤1mm.

[0025] Further, the thickness of the scattering layer positioning grid is L4≤L1 / 2;

[0026] The material of the front shielding grid is tungsten, and when the front shielding grid is sleeved on the scattering detection element, the corresponding hole of the front shielding grid exceeds the top of the corresponding scattering detection element, and the exceeding depth is L3≥a1; a1 is the length of the outer wall cross section of the protective shell.

[0027] Further, the spacing between adjacent scattering detection elements is W≥a1.

[0028] Further, the material of the reflective coating is BaSO4, TiO2 or MgO;

[0029] The photoelectric device is SiPM or MPPC.

[0030] Further, the spacing between the scattering layer array detection module and the absorption layer array detection module is 100mm≥D≥50mm;

[0031] The shielding shell includes a side shielding shell, a rear shielding cover plate and a Be window;

[0032] The side shielding shell includes a scattering layer array mounting frame, a middle conical frame and an absorption layer array mounting frame arranged in sequence from front to back;

[0033] The scattering layer PCB board is installed in the scattering layer array mounting frame, and the top surface of each scattering detection element faces away from the absorbing layer array mounting frame;

[0034] The small end of the middle frustum frame is connected with the scattering layer array mounting frame, and the large end is connected with the absorbing layer array mounting frame;

[0035] The scattering layer array mounting frame and the small end side wall of the middle frustum frame are provided with notches for the scattering layer flexible flat cable plug to extend out;

[0036] The absorbing layer array mounting frame is provided with notches on the side wall for the absorbing layer flexible flat cable plug to extend out;

[0037] The rear shielding cover plate is covered on the rear end opening of the absorbing layer array mounting frame;

[0038] The Be window is installed at the front end opening of the scattering layer array mounting frame.

[0039] Further, the inner wall of the scattering layer array mounting frame is provided with a first limiting installation boss matched with the scattering layer PCB board around the circumference thereof;

[0040] The inner wall of the absorbing layer array mounting frame is provided with a second limiting installation boss matched with the absorbing layer PCB board around the circumference thereof.

[0041] The present application has the following advantages:

[0042] 1. The Compton imaging system suitable for gamma ray detection in a complex radiation field provided by the present application, by setting a front-end detection unit, a front-end electronic control unit and a rear-end data processing and control unit, and setting a scattering layer array detection module and an absorbing layer array detection module in the front-end detection unit, and setting a shielding shell for the scattering layer array detection module and the absorbing layer array detection module, the scattering layer array detection module and the absorbing layer array detection module can provide a better imaging field of view for the system, and the shielding shell can effectively reduce the interference of gamma cameras outside the target field of view on the front-end detection unit, improve the applicability of the Compton imaging system in a complex radiation environment, and further improve the imaging quality.

[0043] 2. The Compton imaging system suitable for gamma ray detection in a complex radiation field provided by the present application, the scattering detection elements in the scattering layer array detection module are provided with a front shielding grid and a scattering layer positioning grid, and the absorbing detection elements are provided with an absorbing layer positioning grid; the front shielding grid and the absorbing layer positioning grid can limit the imaging field of view of the scattering detection elements and the absorbing detection elements to some extent, reduce the incidence of large-angle rays, and on the other hand, under the condition of not affecting the Compton scattering gamma rays reaching the absorbing detection elements as much as possible, the signal crosstalk between the scattering detection elements can be reduced.

[0044] 3. The Compton imaging system for gamma ray detection in a complex radiation field provided by the application, the N*N scattering detection elements and the M*M absorption detection elements are staggered, which can reduce the direct incidence of gamma rays on the absorption detection elements, and further reduce the influence of backscattering events on the imaging effect.

[0045] 4. The Compton imaging system for gamma ray detection in a complex radiation field provided by the application, when the front shielding grid is sleeved on the scattering detection element, the corresponding hole exceeds the top of the corresponding scattering detection element by a depth L3 greater than the outer wall cross-sectional length a1 of the protective shell, which can form good shielding for the absorption detection element.

[0046] 5. The Compton imaging system for gamma ray detection in a complex radiation field provided by the application, the thickness L4 of the scattering layer positioning grid is less than or equal to L1 / 2, which can further reduce the crosstalk between the scattering detection elements, while avoiding significantly reducing the transport efficiency of scattered photons to the absorption detection elements. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 is a structural schematic diagram of an embodiment of the Compton imaging system for gamma ray detection in a complex radiation field provided by the application;

[0048] Figure 2 is a structural schematic diagram of the front-end detection unit in the embodiment of the application;

[0049] Figure 3 is a spacing diagram of the scattering layer array detection module and the absorption layer array detection module in the embodiment of the application;

[0050] Figure 4 is a three-dimensional structural schematic diagram of the shielding shell in the embodiment of the application;

[0051] Figure 5 is a three-dimensional structural schematic diagram of the scattering layer array detection module in the embodiment of the application;

[0052] Figure 6 is an exploded view of the scattering layer array detection module in the embodiment of the application;

[0053] Figure 7 is a structural schematic diagram of the scintillator in the embodiment of the application;

[0054] Figure 8 is a three-dimensional structural schematic diagram of the absorption layer array detection module in the embodiment of the application;

[0055] Figure 9 is an exploded view of the absorption layer array detection module in the embodiment of the application.

[0056] Corresponding reference signs:

[0057] 1-scattering layer array detection module, 11-scattering detection element, 111-scintillator, 112-photoelectric device, 113-reflective coating, 114-protection shell, 115-optical glue, 12-front shielding grid, 13-scattering layer positioning grid, 14-scattering layer PCB board, 15-scattering layer flexible cable plug, 2-absorption layer array detection module, 21-absorption detection element, 22-absorption layer positioning grid, 23-absorption layer PCB board, 24-absorption layer flexible cable plug, 3-shielding shell, 31-side shielding shell, 311-scattering layer array mounting frame, 312-absorption layer array mounting frame, 313-middle conical frame, 314-first limiting installation boss, 315-notch, 32-back shielding cover plate, 33-Be window. DETAILED DESCRIPTION

[0058] The technical solutions of the present application will be described clearly and completely in combination with the drawings and embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, but not all. Based on the embodiments of the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0059] The Compton imaging system provided by the embodiment of the present application is suitable for gamma ray detection in a complex radiation field, as shown in the figure, comprising a front-end detection unit, a front-end electronic control unit and a back-end data processing and control unit; the back-end data processing and control unit is located in the upper computer in the embodiment. Figure 1

[0060] As shown in the figure, the front-end detection unit comprises a shielding shell 3, and a scattering layer array detection module 1 and an absorption layer array detection module 2 arranged in parallel in the shielding shell 3; the scattering layer array detection module 1 and the absorption layer array detection module 2 are used for receiving gamma rays and converting them into corresponding detection information. Figure 2

[0061] As shown in the figure, the spacing D between the scattering layer array detection module 1 and the absorption layer array detection module 2 can be adjusted according to the position resolution and detection efficiency requirements; the larger the value of D is, the better the position resolution is, but the lower the detection efficiency is; in order to ensure good imaging effect, in the embodiment, 100mm≥D≥50mm. Figure 3

[0062] As shown in the figure, the spacing D between the scattering layer array detection module 1 and the absorption layer array detection module 2 can be adjusted according to the position resolution and detection efficiency requirements; the larger the value of D is, the better the position resolution is, but the lower the detection efficiency is; in order to ensure good imaging effect, in the embodiment, 100mm≥D≥50mm. Figure 2 Figure 4 ​​​​As shown, the shielding shell 3 includes a side shielding shell 31, a rear shielding cover plate 32 and a Be window 33; the side shielding shell 31 includes a scattering layer array mounting frame 311, a middle frustum frame 313 and an absorbing layer array mounting frame 312 arranged in sequence from front to back; the small end of the middle frustum frame 313 is connected with the scattering layer array mounting frame 311, and the large end is connected with the absorbing layer array mounting frame 312; the rear shielding cover plate 32 is covered on the opening of the absorbing layer array mounting frame 312; and the Be window 33 is installed on the opening of the scattering layer array mounting frame 311.

[0063] The thickness H of the side shielding shell 31 and the rear shielding cover plate 32 is greater than or equal to 15 mm, and the attenuation coefficient of 662KeV rays is about 10 times, and the thickness can be appropriately increased in a higher radiation intensity environment.

[0064] As shown in Figure 5 and Figure 6 As shown, the scattering layer array detection module 1 includes a scattering layer PCB board 14, N×N arrayed scattering detection elements 11 on the scattering layer PCB board 14, a scattering layer positioning grid 13 and a front shielding grid 12 sleeved on the N×N scattering detection elements 11; N≥8; in this embodiment, N=8; 8×8 scattering detection elements 11 are welded on the same scattering layer PCB board 14, the scattering layer PCB board 14 is installed in the scattering layer array mounting frame 311, and the top surface of each scattering detection element 11 faces away from the absorbing layer array mounting frame 312; the scattering layer PCB board 14 is provided with a scattering layer flexible cable plug 15 for connecting with a front-end electronic control unit, and the scattering layer PCB board 14 further includes necessary circuits for SiPM power supply and signal reading. The small end of the scattering layer array mounting frame 311 and the middle frustum frame 313 is provided with a notch for the scattering layer flexible cable plug 15 to extend out; and the inner wall of the scattering layer array mounting frame 311 is provided with a first limiting mounting boss 314 matching the scattering layer PCB board 14 around the circumference.

[0065] The front shielding grid 12 has N×N square holes, and the grid holes correspond one by one to the scattering detection elements 11; the main function is to limit the imaging field of view to a certain extent, reduce the incidence of large-angle rays, and reduce the signal crosstalk between the scattering detection elements 11 under the condition of not affecting the Compton scattered gamma rays reaching each absorbing detection element 21 as much as possible.

[0066] The scattering layer positioning grid 13 is located between the scattering layer PCB board 14 and the front shielding grid 12; the positioning grid 13 has 8x8 holes, which need to be processed with high precision, so that the grid holes are one-to-one corresponding to the scattering detection elements 11 and completely matched with the scattering layer PCB board 14, protecting the scattering detection elements 11, ensuring the close coupling of the scintillator 111 and the photoelectric device 112 and preventing it from being de-soldered from the scattering layer PCB board 14. The thickness of the scattering layer positioning grid 13 is adjusted according to the matching condition combined with the parameters of the front shielding grid 12.

[0067] In order to effectively reduce the cross talk between the scattering detection elements 11, while avoiding significantly reducing the transport of scattered photons to the absorption detection elements 21, the scattering layer positioning grid 13 is made of polyethylene.

[0068] As shown in Figure 7 The scattering detection element 11 includes a photoelectric device 112 mounted on the scattering layer PCB board 14, a scintillator 111 coupled to the photoelectric device 112 on the bottom surface through optical glue 115, a reflective coating 113 coated on the side and top of the scintillator 111, and a protective shell 114 sleeved outside the reflective coating 113; the scintillator 111 is a quadrangular prism structure, and all six outer surfaces are mirror polished;

[0069] The height from the bottom surface to the top surface of the scintillator 111 is L1, and 4mm≤L1≤7mm; the cross section of the scintillator 111 is a square, the side length of the square is a, and 2mm≤a≤4mm, L1>a; the bottom surface of the scintillator 111 without coating serves as a light emitting surface; the light emitting surface of the scintillator 111 is coupled with the photoelectric device 112 through high-transmittance optical glue 115, so that the fluorescence excited by radiation of the scintillator 111 is transmitted to the photosensitive surface of the photoelectric device 112 as much as possible. In this embodiment, the scintillator 111 is any one of CsI, GAGG or LYSO crystal materials; in order to match the standard photosensitive area of the photoelectric device 112, a=3mm; the thickness L4 of the scattering layer positioning grid 13 is ≤L1 / 2.

[0070] The photoelectric device 112 is SiPM or MPPC; in this embodiment, MicroFC-30035-SMT of onsemi company is used.

[0071] The reflective coating 113 uses a coating with high reflectivity, and the material of the reflective coating 113 specifically uses any one of BaSO4, TiO2 or MgO, and the thickness of the reflective coating 113 reaches 0.08mm-0.12mm, so that the reflectivity is ≥90%;

[0072] The protective housing 114 is made of aluminum or Teflon; the thickness h of the protective housing 114 is ≤1mm. After the scintillator 111 is coupled to the optoelectronic device 112, it is encapsulated with a thin protective housing 114 made of aluminum or Teflon to protect the reflective coating 113 and ensure the firm coupling between the scintillator 111 and the optoelectronic device 112. The thickness of the encapsulated protective housing 114 is not greater than 1mm.

[0073] Optical adhesive 115 has a refractive index ≥1.5 to reduce the total internal reflection angle of incident light.

[0074] The front shielding grid 12 is made of tungsten. When the front shielding grid 12 is mounted on the scattering detection element 11, its corresponding holes extend beyond the top of the corresponding scattering detection element 11. In order to limit the field of view, the depth of extension L3 ≥ a1; a1 is the side length of the outer wall cross-section of the protective shell 114.

[0075] The specific values ​​of L3 and L4 can be adjusted according to the detection field of view, detection efficiency, and the requirements of the environment to be tested.

[0076] To achieve a good shielding effect on the absorption layer, the spacing W between adjacent scattering detection elements 11 should be greater than or equal to a1.

[0077] like Figure 8 and Figure 9 As shown, the absorption layer array detection module 2 does not have a shielding grid structure; it is only protected by the positioning grid 22 for the absorption detection element 21. Specifically, the absorption layer array detection module 2 includes an absorption layer PCB board 23, M×M absorption detection elements 21 arranged in an array on the absorption layer PCB board 23, and an absorption layer positioning grid 22 fitted onto the M×M absorption detection elements 21. To improve detection efficiency, M > N. The absorption layer PCB board 23 is provided with an absorption layer flexible flat cable connector 24 for connection with the front-end electronic control unit. The absorption layer array mounting frame 312 is provided with a notch 315 for the absorption layer flexible flat cable connector 24 to extend. The inner wall of the absorption layer array mounting frame 312 is provided with a second limiting mounting boss that matches the absorption layer PCB board 23 around its circumference.

[0078] The scattering layer array detector module 1 and the absorption layer array detector module 2 are distributed one after the other on the same axis, so that the N×N scattering detector elements 11 and the M×M absorption detector elements 21 are staggered. The purpose is to reduce the direct incidence of gamma rays on the absorption detector elements 21, thereby reducing the impact of backscattering on the imaging effect.

[0079] The structure of the absorption detector element 21 is the same as that of the scattering detector element 11. Considering the position resolution and detection efficiency of the array, the height from the bottom surface to the top surface of the scintillator in the absorption detector element 21 is L2, 8mm≤L2≤12mm.

[0080] The front-end electronic control unit comprises a signal processing module, a communication module and a control module; the input end of the signal processing module is connected with the scattering layer array detection module 1 and the absorbing layer array detection module 2 respectively, the output end thereof is connected with the input end of the communication module, the output end of the communication module is connected with the input end of the signal processing module and the input end of the back-end data processing and control unit respectively; the control module is connected with the communication module; the signal processing module is used for receiving detection information and extracting effective Compton events from the detection information, and sends the effective Compton events to the back-end data processing and control unit through the communication module under the control of the control module; the communication module is used for information transmission between the signal processing module and the back-end data processing and control unit.

[0081] The main components of the signal processing module are an ASIC chip and a field programmable gate array (FPGA) chip. The ASIC chip collects N*N signals from the scattering layer array detection module 1 and M*M signals from the absorbing layer array detection module 2. The signals collected by the ASIC chip are received by the FPGA chip, effective Compton events are extracted by time coincidence measurement, and the information such as event time, amplitude and position is uploaded to the back-end data processing and control software through the control and communication module.

[0082] The control module and the communication module are responsible for data and instruction transmission between the FPGA and the host computer, and control the working state of the front-end detection unit and the signal processing module through the FPGA.

[0083] In the embodiment, the data processing and control unit is connected with the front-end electronic control unit through a network cable to realize interaction with the front end. The data processing and control unit block can set measurement and signal acquisition parameters, further filter and distinguish Compton imaging event information obtained by measurement, and use imaging methods including but not limited to back-projection reconstruction algorithm and iterative reconstruction algorithm to realize imaging of the radiation source and display the final result.

[0084] The above merely describes specific embodiments of the present application, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A Compton imaging system suitable for gamma-ray detection in complex radiation fields, characterized in that: The system comprises a front-end detection unit, a front-end electronic control unit and a back-end data processing and control unit. The front-end detection unit comprises a shielding shell (3), a scattering layer array detection module (1) and an absorbing layer array detection module (2) arranged in parallel in the shielding shell (3). The scattering layer array detection module (1) and the absorbing layer array detection module (2) are used for receiving gamma rays and converting them into corresponding detection information. The front-end electronic control unit comprises a signal processing module, a communication module and a control module. The input end of the signal processing module is connected with the output end of the scattering layer array detection module (1) and the absorbing layer array detection module (2) respectively, the output end of the signal processing module is connected with the input end of the communication module, the output end of the communication module is connected with the input end of the signal processing module and the input end of the back-end data processing and control unit respectively, and the control module is connected with the communication module. The signal processing module is used for receiving the detection information, extracting effective Compton events from the detection information, and sending the effective Compton events to the back-end data processing and control unit through the communication module under the control of the control module.

2. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 1, wherein: The scattering layer array detection module (1) comprises a scattering layer PCB board (14), N×N arrayed scattering detection elements (11) on the scattering layer PCB board (14), a scattering layer positioning grid (13) sleeved on the N×N scattering detection elements (11) and a front shielding grid (12); N≥8; the scattering layer positioning grid (13) is located between the scattering layer PCB board (14) and the front shielding grid (12); the scattering layer PCB board (14) is provided with a scattering layer flexible flat cable plug (15) used for being connected with the front-end electronic control unit; the output ends of the N×N scattering detection elements (11) are respectively connected with corresponding terminals of the scattering layer flexible flat cable plug (15); The absorbing layer array detection module (2) comprises an absorbing layer PCB board (23), M×M arrayed absorbing detection elements (21) on the absorbing layer PCB board (23) and an absorbing layer positioning grid (22) sleeved on the M×M absorbing detection elements (21); M>N; the absorbing layer PCB board (23) is provided with an absorbing layer flexible flat cable plug (24) used for being connected with the front-end electronic control unit; the output ends of the M×M absorbing detection elements (21) are respectively connected with corresponding terminals of the absorbing layer flexible flat cable plug (24); The N×N scattering detection elements (11) and the M×M absorbing detection elements (21) are arranged in a staggered manner.

3. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 2, wherein: The scattering detection element (11) comprises a photoelectric device (112) mounted on a scattering layer PCB board (14), a scintillator (111) coupled to the photoelectric device (112) by optical glue (115) on the bottom surface, a reflective coating (113) coated on the side and top of the scintillator (111), and a protective shell (114) sleeved outside the reflective coating (113); The scintillator (111) is in a quadrangular prism structure, and the cross section of the scintillator (111) is a square with a side length of a, and 2mm≤a≤4mm; The thickness of the reflective coating (113) is 0.08mm-0.12mm; The structure of the absorption detection element (21) is the same as that of the scattering detection element (11); The height of the scintillator (111) of the scattering detection element (11) from the bottom surface to the top surface is L1, and 4mm≤L1≤7mm; the output end of the photoelectric device (112) of the scattering detection element (11) is connected with the corresponding terminal of the scattering layer flexible cable plug (15); The height of the scintillator (111) of the absorption detection element (21) from the bottom surface to the top surface is L2, and 8mm≤L2≤12mm; the output end of the photoelectric device (112) of the absorption detection element (21) is connected with the corresponding terminal of the absorption layer flexible cable plug (24).

4. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 3, characterized in that: a = 3mm; The scintillator (111) is CsI, GAGG or LYSO.

5. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 4, characterized in that: The protective shell (114) is made of aluminum or Teflon material; The thickness of the protective shell (114) is h≤1mm.

6. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 5, characterized in that: The thickness of the scattering layer positioning grid (13) is L4≤L1 / 2; The material of the front shielding grid (12) is tungsten, and when the front shielding grid (12) is sleeved on the scattering detection element (11), the corresponding hole of the front shielding grid (12) exceeds the top of the corresponding scattering detection element (11) by a depth L3≥a1; a1 is the cross-sectional side length of the outer wall of the protective shell (114).

7. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 6, characterized in that: The spacing between adjacent scattering detection elements (11) is W≥a1.

8. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 7, characterized in that: The material of the reflective coating (113) is BaSO4, TiO2 or MgO; The photoelectric device (112) is SiPM or MPPC.

9. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to any one of claims 2-8, characterized in that: The spacing between the scattering layer array detection module (1) and the absorption layer array detection module (2) is 100mm≥D≥50mm. The shielding shell (3) comprises a side shielding shell (31), a back shielding cover plate (32) and a Be window (33); The side shielding shell (31) comprises a scattering layer array mounting frame (311), a middle conical frame (313) and an absorbing layer array mounting frame (312) arranged in sequence from front to back; The scattering layer PCB board (14) is mounted in the scattering layer array mounting frame (311), and the top surface of each scattering detection element (11) faces away from the absorbing layer array mounting frame (312); The small end of the middle conical frame (313) is connected with the scattering layer array mounting frame (311), and the large end is connected with the absorbing layer array mounting frame (312); The small end side wall of the scattering layer array mounting frame (311) and the middle conical frame (313) is provided with a notch for the scattering layer flexible flat cable plug (15) to extend out; The side wall of the absorbing layer array mounting frame (312) is provided with a notch (315) for the absorbing layer flexible flat cable plug (24) to extend out; The back shielding cover plate (32) is covered at the rear end opening of the absorbing layer array mounting frame (312); The Be window (33) is mounted at the front end opening of the scattering layer array mounting frame (311).

10. The Compton imaging system suitable for gamma ray detection in a complex radiation field according to claim 9, characterized in that: The inner wall of the scattering layer array mounting frame (311) is provided with a first limiting mounting boss (314) matched with the scattering layer PCB board (14) around the circumference thereof; The inner wall of the absorbing layer array mounting frame (312) is provided with a second limiting mounting boss matched with the absorbing layer PCB board (23) around the circumference thereof.

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