Multi-opening coding aperture imaging device and method

Abstract

The invention discloses a multi-opening coding aperture imaging device and method. The multi-opening coding aperture imaging device comprises a high-current accelerator, a scattering target, a coding module, an imaging module and a shielding collimation system, the coding module and the imaging module are located in the shielding collimation system, the high-current accelerator, the scattering target, the coding module and the imaging module are sequentially distributed, and the device and the method can achieve a high-quality imaging effect in a complex radiation environment.

Description

Technical Field

[0001] The invention belongs to the field of high-dose rate strong pulse gamma radiation environment diagnosis, and relates to a multi-opening coded aperture imaging device and method. Background Art

[0002] Accurate measurement of radiation dose field distribution is crucial for accurate simulation of strong pulse radiation environment parameters and evaluation of dose rate damage effects on electronic devices and systems. Strong pulse gamma radiation environment is usually generated by bombarding high atomic number targets with strong pulse electron beams. It is characterized by narrow pulse width (half-maximum width is only 20ns) and high particle yield (the number of gamma photons reaches 3.4×10 16 / pulse) and is accompanied by a complex mixed radiation field of electrons and neutrons, making it difficult for conventional measurement methods to achieve high-precision measurements in this environment.

[0003] Traditional measurement methods, such as thermoluminescent dosimeters, can record radiation doses cumulatively, but their spatial resolution is limited and they require manual quenching to read data. The measurement time cost is too high, which limits their application in high-dose-rate intense pulse radiation environments. In addition, detectors such as scintillators and semiconductors need to be placed in the pulse radiation field area, which are prone to severe saturation in high-dose-rate environments and cannot meet the requirements of detector sensitivity and range dynamic range. In recent years, a method has been proposed that uses thin target scattering to reduce the intensity of gamma rays and uses pinhole photography technology to measure the intensity distribution of intense pulse gamma radiation dose fields. However, pinhole imaging has the disadvantages of low detection efficiency, large statistical fluctuations of rays, and sensitivity to noise, and shows significant limitations in intense pulse gamma radiation environments. Therefore, how to achieve fast and accurate dose distribution measurement in complex intense pulse gamma radiation fields has become an important research topic in this field.

[0004] Chinese patent 201811168588.6 proposes a method for measuring and diagnosing the dose field distribution of intense pulsed gamma radiation. This method arranges a thin scattering target behind the anode target of an intense current accelerator to scatter 3 to 10% of the pulsed gamma-ray beam photons, then uses a pinhole camera system to generate a latent image on the imaging plate, and finally reconstructs the dose field intensity distribution by non-negative linear least squares method. However, the gamma photons drawn out from the beam outlet of the intense current accelerator have a continuous spectrum of 0 to 10 MeV. The existing pinhole camera system can only accept gamma photons from a specific scattering angle due to its fixed and single opening, and cannot adapt to the dependence of energy on the scattering angle (high-energy gamma photons tend to scatter at small angles, and low-energy gamma photons tend to diverge at large angles), resulting in insufficient detection coverage and loss of imaging information in the camera system, affecting the accurate measurement of the overall dose field distribution. In addition, the non-negative linear least squares method as a reconstruction method has shortcomings in convergence speed, noise resistance, and the ability to restore edges and details, which limits its reconstruction accuracy in complex and high-noise environments. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a multi-opening coded aperture imaging device and method, which can achieve high-quality imaging effects in a complex radiation environment.

[0006] To achieve the above-mentioned object, the present invention discloses a multi-opening coded aperture imaging device, comprising a high-current accelerator, a scattering target, a coding module, an imaging module and a shielding collimation system;

[0007] The encoding module and the imaging module are located in the shielding and collimating system, and the high-current accelerator, the scattering target, the encoding module and the imaging module are distributed in sequence.

[0008] Furthermore, the encoding module is a multi-opening encoding aperture.

[0009] Furthermore, the multi-opening coded aperture is provided with three openings, and the centers of the openings are respectively at angles of 20 degrees, 30 degrees and 40 degrees with the center of the scattering target.

[0010] Furthermore, the imaging module is an IP imaging board.

[0011] Furthermore, it also includes a capture hole system, which is installed behind the IP imaging board.

[0012] Furthermore, the distance between the scattering target and the anode target in the high-current accelerator is 3-5 cm.

[0013] Furthermore, the acceleration front end of the high-current accelerator generates, modulates and pre-accelerates the particle beam, and the strong pulse radiation gamma photons emitted from the beam output end have a continuous spectrum of 0 to 10 MeV.

[0014] The present invention discloses a multi-opening coded aperture imaging method, comprising the following steps:

[0015] 1) Gamma photons generated by the high-intensity accelerator are directed toward the scattering target and scattered, causing the direction of the gamma photons to deviate from the original radiation beam direction;

[0016] 2) The scattered gamma photons enter the shielded collimation system, are then encoded by the multi-opening coded aperture, and then deposit energy on the IP imaging plate to form a two-dimensional latent image;

[0017] 3) Record the energy distribution of gamma photons through the IP imaging plate, and then reconstruct the reconstructed dose field intensity distribution at the scattering target;

[0018] 4) Determining a dose distribution diagram of an intense pulsed gamma radiation field according to the reconstructed dose field intensity distribution.

[0019] Further, a coding image g is generated according to the two-dimensional latent image;

[0020] A source image distribution f is generated according to a point spread function h of an imaging system and a coded image g, and the source image distribution f is used as a reconstructed dose field intensity distribution at a scattering target.

[0021] Furthermore, the imaging process satisfies the degradation model as follows:

[0022] g=h*f+n

[0023] Among them, g is the encoded image, h is the point spread function, f is the source image distribution, n is the noise term, and * represents convolution.

[0024] The present invention has the following beneficial effects:

[0025] The multi-aperture coded aperture imaging device and method described in the present invention adopt a multi-aperture coded aperture design during specific operation, and can simultaneously receive gamma photons from different scattering angles, overcome the limitation of a single fixed aperture of a pinhole camera system in capturing gamma photons of different energies, and improve the comprehensive perception of complex gamma-ray fields and the accuracy of dose field distribution measurement; in addition, the multi-aperture coded aperture is placed in a shielded collimation system. Compared with a traditional pinhole imaging system, the present invention has higher detection efficiency and certain tomographic imaging capabilities, and has a reasonable structural design. It can achieve high-precision dose field intensity distribution measurement in a limited space under the premise of having little impact on the strong pulse radiation field environment of the experimental area, thereby achieving high-quality imaging effects in a complex radiation environment.

[0026] Furthermore, the present invention is provided with a capture hole system, which can effectively reduce the background noise and electromagnetic interference of multiple particles in the mixed radiation field of electrons and neutrons, improve the signal-to-noise ratio of the IP imaging board, and ensure the imaging quality.

[0027] Furthermore, the multi-opening design of the coded aperture of the device can receive gamma photons from different angles, significantly improving the detection efficiency. At the same time, since the system magnification and point spread function corresponding to the source points at different distances from the coded aperture are different, the position information is actually included in the coded image, thereby achieving depth resolution to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings:

[0029] Figure 1 A perspective view of the present invention;

[0030] Figure 2 It is a structural diagram of the present invention;

[0031] Figure 3 1 is a structural diagram of a multi-opening coded aperture 3 in an embodiment of the present invention, a is a left view of the multi-opening coded aperture 3; b is a cross-sectional view of the multi-opening coded aperture 3;

[0032] Figure 4 Schematic diagram of the “E”-shaped source a constructed by simulation of the present invention and the reconstruction result b of the “E”-shaped source.

[0033] Among them, 1 is a high-current accelerator, 1-1 is an acceleration front end, 1-2 is a beam output end, 2 is a scattering target, 3 is a multi-opening coded aperture, 4 is an IP imaging plate, 5 is a capture hole system, and 6 is a shielded collimation system. DETAILED DESCRIPTION

[0034] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] In the description of the present invention, it should be understood that the terms “include” and “comprises” indicate the presence of described features, wholes, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components and / or collections thereof.

[0036] It should also be understood that the terms used in the present specification are only for the purpose of describing specific embodiments and are not intended to limit the present invention. As used in the present specification and the appended claims, unless the context clearly indicates otherwise, the singular forms "a", "an" and "the" are intended to include plural forms.

[0037] It should be further understood that the term "and / or" used in the present specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in the present invention generally indicates that the associated objects are in an "or" relationship.

[0038] It should be understood that, although the terms first, second, third, etc. may be used to describe preset ranges, etc. in the embodiments of the present invention, these preset ranges should not be limited to these terms. These terms are only used to distinguish preset ranges from each other. For example, without departing from the scope of the embodiments of the present invention, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0039] The word "if" as used herein may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting", depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to determining" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)", depending on the context.

[0040] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. The components of the embodiments of the present invention described and shown in the drawings here can usually be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Various structural schematic diagrams of the embodiments disclosed in the present invention are shown in the accompanying drawings. These figures are not drawn to scale, and some details are magnified and some details may be omitted for the purpose of clear expression. The shapes of various regions and layers shown in the figures and the relative sizes and positional relationships therebetween are only exemplary, and may deviate in practice due to manufacturing tolerances or technical limitations, and those skilled in the art may additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0042] Embodiment 1

[0043] refer to Figure 1 and Figure 2 The multi-opening coded aperture imaging device of the present invention comprises a high-current accelerator 1, a scattering target 2, a multi-opening coded aperture 3, an IP imaging plate 4, a capture hole system 5 and a shielding collimation system 6;

[0044] The multi-opening coded aperture 3 and the IP imaging plate 4 are located in the shielding and collimation system 6, and the scattering target 2 is located between the high-current accelerator 1 and the shielding and collimation system 6. The strong pulse radiation gamma photons output by the high-current accelerator 1 bombard the scattering target 2, causing the scattering target 2 to emit gamma photons, which pass through the multi-opening coded aperture 3 and are incident on the IP imaging plate 4.

[0045] In this embodiment, a capture hole system 5 is further included, wherein the shielding collimation system 6 is located between the capture hole system 5 and the scattering target 2 .

[0046] In this embodiment, the acceleration front end 1-1 of the high-current accelerator 1 generates, modulates and pre-accelerates a particle beam, and the high-intensity pulse radiation gamma photons emitted from the beam outlet end 1-2 have a continuous spectrum of 0 to 10 MeV.

[0047] In this embodiment, the material selected for the scattering target 2 is copper, tungsten, aluminum or stainless steel. The thickness of the scattering target 2 of different materials is different. The distance between the scattering target 2 and the anode target in the high-current accelerator 1 is 3-5 cm, and the scattering target 2 is parallel to the anode target, and the scattering target 2 is perpendicular to the direction of the ray beam.

[0048] In this embodiment, the material of the multi-opening coded aperture 3 is lead, and the multi-opening coded aperture 3 can simultaneously receive gamma photons from different scattering angles. The IP imaging plate 4 is placed at the rear side of the multi-opening coded aperture 3, and the dose intensity scattered by the scattering target 2 is within the dynamic range of the IP imaging plate 4, and the IP imaging plate 4 has a good response to the gamma photons in this energy range. The multi-opening coded aperture 3 and the IP imaging plate 4 are located in the shielded collimation system 6.

[0049] In this embodiment, the shielding and collimation system 6 adopts a composite material optimized design. The outer layer of the shielding and collimation system 6 is made of boron-containing polyethylene for absorbing neutrons; the middle layer of the shielding and collimation system 6 is made of lead or tungsten to effectively shield high-energy gamma photons; the inner layer of the shielding and collimation system 6 is made of a stainless steel bracket to ensure structural strength.

[0050] In this embodiment, the capture hole system 5 is installed behind the IP imaging plate 4 to further reduce the influence of gamma photons that do not pass through the multi-opening coded aperture 3 on the imaging data.

[0051] In this embodiment, a design similar to an array pinhole is adopted. According to the experimental conditions and the working state of the high-current accelerator 1, the multi-opening coded aperture 3 can be replaced by an array ring hole or a combination of an array ring hole and a pinhole.

[0052] Preferably, the IP imaging plate 4 can be replaced by a highly sensitive CZT (cadmium zinc telluride) detector or CdTe (cadmium telluride) detector, so that the system further has time resolution capability. The capture hole system 5 can be replaced by a scintillator material (such as NaI (Tl) or LaBr3) and a photomultiplier tube array.

[0053] Embodiment 2

[0054] Accordingly, the multi-opening coded aperture imaging method of the present invention adopts an RL reconstruction algorithm to obtain the dose field intensity distribution at the scattering target 2. Since the scattered gamma dose field intensity distribution at the scattering target 2 is consistent with the dose field intensity distribution of the intense pulsed gamma radiation field, the dose field distribution of the reconstructed intense pulsed gamma radiation field is given, and the steps include:

[0055] 1) The strong pulsed gamma photons generated by the acceleration front end 1-1 of the high-current accelerator 1 are directed toward the scattering target 2, where they are scattered, causing the direction of the gamma photons to deviate from the original radiation beam direction;

[0056] 2) The scattered gamma photons enter the shielding collimation system 6 which is about 30 to 150 cm away from the scattering target 2. After shielding and collimation, the flux of the gamma photons is reduced by 3 to 4 orders of magnitude, and then they are encoded by the multi-opening coded aperture 3 and deposit energy on the IP imaging plate 4 to form a two-dimensional latent image.

[0057] 3) Reconstruct the intensity distribution of the gamma dose field through the RL algorithm to generate a dose field distribution map. In this embodiment, the imaging process satisfies the degradation model:

[0058] g=h*f+n

[0059] Among them, g is the coded image, h is the point spread function, f is the source image distribution, n is the noise term, * represents convolution, RL is a nonlinear iterative algorithm, I iis the ideal noise-free signal distribution after being transmitted by the imaging system, then:

[0060]

[0061] Among them, h i,j is the point spread function of the imaging system, f j is the source image, when the actual image g after taking into account the noise satisfies the parameter I i Poisson distribution, then the joint likelihood function L of g can be expressed as:

[0062]

[0063] The requirements for lnL to take extreme values ​​are:

[0064]

[0065] When the point spread function satisfies the linear invariance approximation, we get

[0066]

[0067] Among them, ||h|| represents the sum of all elements of h. For images whose noise distribution obeys Poisson distribution and Gaussian distribution, the RL algorithm can converge to the maximum likelihood solution. When the number of iterations of the RL algorithm is too large, it will cause noise amplification, which is easy to cause false edges and star point artifacts. Generally, 50 iterations are taken.

[0068] In the embodiment, the coded image g is generated by the two-dimensional latent image obtained by the IP imaging plate 4, and then the corresponding point spread function h is obtained by MCNP simulation calculation. In MATLAB, the source image distribution f can be obtained by solving the coded image g and the point spread function h.

[0069] 4) The scattered gamma dose field intensity distribution at the IP imaging plate 4 is consistent with the dose field intensity distribution of the strong pulsed gamma radiation field. The source image distribution obtained by the iteration of the RL algorithm is the reconstructed dose field intensity distribution at the scattering target 2. The dose field distribution of the strong pulsed gamma radiation field can be given based on the reconstruction result.

[0070] In the embodiment, the multi-opening coded aperture 3 is provided with three openings, the centers of which are at angles of 20 degrees, 30 degrees and 40 degrees to the center of the scattering target 2, respectively. The left view and the cross-sectional view are as follows: Figure 3 (a) and Figure 3 (b) The central angle of the pinhole remains fixed, but its field of view can cover a wider range of gamma photon scattering angles, covering most of the scattering angles of gamma photons in the energy range of 0 to 10 MeV.

[0071] The opening size of the multi-opening coded aperture 3 can be further optimized according to the scattering characteristics of gamma photons and experimental requirements to ensure that the imaging accuracy and spatial resolution meet the experimental requirements.

[0072] In the embodiment, the simulation defines an "E"-shaped source to characterize the complex source region structure of the strong gamma radiation field. The source image is as follows: Figure 4 (a) shows the reconstruction result. Figure 4 As shown in (b), it can be seen that the reconstructed image is clear and successfully reflects the structural characteristics of the original source, indicating that the present invention has good reconstruction accuracy in the gamma radiation field of complex source region structure.

[0073] Embodiment 3

[0074] A computer device includes a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the multi-opening coded aperture imaging method are implemented. The memory may include a memory, such as a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk memory, etc. The processor, the network interface, and the memory are interconnected through an internal bus. The internal bus may be an industrial standard architecture bus, a peripheral component interconnection standard bus, an extended industrial standard structure bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory may include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0075] Embodiment 4

[0076] A computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the multi-opening coded aperture imaging method are implemented. Specifically, the computer-readable storage medium includes, but is not limited to, volatile memory and / or non-volatile memory. The volatile memory may include random access memory (RAM) and / or cache memory, etc. The non-volatile memory may include read-only memory (ROM), hard disk, flash memory, optical disk, magnetic disk, etc.

[0077] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment in combination with software and hardware. Moreover, the present application may adopt the form of a computer program product implemented in one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) that include computer-usable program code.

[0078] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0079] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0080] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0081] Those skilled in the art will readily appreciate other embodiments of the present invention after considering the specification and disclosure of the invention. This application is intended to cover any variations, uses or adaptations of the present invention that follow the general principles of the present invention and include common knowledge or customary techniques in the art that are not disclosed by the present invention. The specification and examples are to be considered exemplary only, and the true scope and spirit of the present invention are indicated by the following claims.

[0082] It should be understood that the present invention is not limited to the exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

[0083] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural change made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A multi-aperture coded aperture imaging device, characterized in that: It comprises a high-current accelerator (1), a scattering target (2), a coding module, an imaging module and a shielding collimation system (6); The encoding module and the imaging module are located in the shielding collimation system (6), and the high-current accelerator (1), the scattering target (2), the encoding module and the imaging module are distributed in sequence.

2. The multi-aperture coded aperture imaging device according to claim 1, characterized in that: The encoding module is a multi-opening encoding aperture (3).

3. The multi-aperture coded aperture imaging device according to claim 1, characterized in that: The multi-opening coded aperture (3) is provided with three openings, the centers of the openings respectively form angles of 20 degrees, 30 degrees and 40 degrees with the center of the scattering target (2).

4. The multi-aperture coded aperture imaging device according to claim 2, characterized in that: The imaging module is an IP imaging board (4).

5. The multi-aperture coded aperture imaging device according to claim 1, characterized in that: It also includes a capture hole system (5), which is installed behind the IP imaging plate (4).

6. The multi-aperture coded aperture imaging device according to claim 1, characterized in that: The distance between the scattering target (2) and the anode target in the high-current accelerator (1) is 3-5 cm.

7. The multi-aperture coded aperture imaging device according to claim 1, characterized in that: The acceleration front end (1-1) of the high-current accelerator (1) generates, modulates and pre-accelerates a particle beam, and the high-intensity pulse radiation gamma photons emitted by the beam output end (1-2) have a continuous spectrum of 0 to 10 MeV.

8. A multi-opening coded aperture imaging method, characterized in that: The multi-aperture coded aperture imaging device according to claim 3 comprises the following steps: 1) Gamma photons generated by the high-intensity accelerator (1) are directed toward the scattering target (2), where they are scattered, causing the direction of the gamma photons to deviate from the original radiation beam direction; 2) The scattered gamma photons enter the shielded collimation system (6), are then encoded by the multi-opening coded aperture (3), and then deposit energy on the IP imaging plate (4) to form a two-dimensional latent image; 3) recording the energy distribution of gamma photons through the IP imaging plate (4), and then reconstructing the reconstructed dose field intensity distribution at the scattering target (2); 4) Determining a dose distribution diagram of an intense pulsed gamma radiation field according to the reconstructed dose field intensity distribution.

9. The multi-aperture coded aperture imaging method according to claim 8, characterized in that: Generate a coded image g according to the two-dimensional latent image; A source image distribution f is generated according to a point spread function h of an imaging system and a coded image g, and the source image distribution f is used as a reconstructed dose field intensity distribution at a scattering target (2).

10. The multi-aperture coded aperture imaging method according to claim 9, characterized in that: The imaging process satisfies the degradation model: g=h*f+n Among them, g is the encoded image, h is the point spread function, f is the source image distribution, n is the noise term, and * represents convolution.

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