Single-layer Compton camera system and imaging method

Abstract

The invention discloses a single-layer Compton camera system and an imaging method, and relates to the technical field of nuclear radiation imaging. The system comprises a single-plane pixel type gamma ray detector used for collecting gamma ray interaction event data, including time information and energy information of each interaction and two-dimensional position information in a detector plane, and forming pixel counting distribution; the shielding structure is arranged on one side of the plane of the detector, is located in a local area of the detector and is used for enabling pixel counting distribution to generate a local counting missing feature when gamma rays are incident from one side where the shielding structure is located; and the judging and imaging module is used for judging a gamma ray incident side based on the local counting missing feature and executing Compton imaging reconstruction in a corresponding hemispherical view field range according to the judged incident side. According to the invention, partitioned omnidirectional imaging can be carried out on the radioactive source under the condition that a detector does not need to act on depth information, and meanwhile, generation of mirror image artifacts is avoided.

Description

Technical Field

[0001] This invention relates to the field of nuclear radiation imaging technology, and in particular to a single-layer Compton camera system and imaging method. Background Technology

[0002] The Compton camera is a passive gamma-ray imaging device widely used in astrophysical observation, nuclear medicine imaging, nuclear industry flaw detection, and nuclear safety monitoring. Utilizing the Compton scattering principle, the Compton camera inverts the directional distribution of a radiation source by recording the position and energy of the two interactions—Compton scattering and subsequent photoelectric absorption—of a single photon within a coincidence time window.

[0003] Traditional Compton cameras typically employ a "two-layer" or "multi-layer" detector structure: the front layer acts as a Compton scatterer, and the rear layer as a photoelectric absorber. This structure makes it relatively easy to distinguish the direction of photon incidence, but requires two or more detection planes, resulting in a large system size. To improve system compactness, "single-layer" Compton cameras have emerged in recent years, using a single detector volume to record two interactions. Single-layer Compton cameras are usually composed of an integrated three-dimensional position-sensitive detector, capable of acquiring the three-dimensional coordinates of each interaction, thus achieving omnidirectional imaging.

[0004] However, for planar pixelated detectors that only possess photon two-dimensional position readout capability and lack the ability to acquire interaction depth information, the two interaction points of a Compton event are only located on the detector plane, and their depth coordinates are unknown. This leads to a "mirror image" ambiguity problem: when the radiation source is located on one side of the detector plane, the coincidence event it produces is indistinguishable from the coincidence event from a radiation source at a mirror-symmetrical position on the opposite side under ideal geometry. This results in both true sources and mirror-image spurious sources appearing simultaneously at symmetrical positions on both sides of the detector in the reconstructed image. This mirror image artifact severely affects the accuracy of the imaging results.

[0005] In existing technologies, to avoid mirror-image ambiguity, the common practice is to pre-fix the imaging field of view to one side of the detector, for example, assuming the radiation source is only in the half-space above the detector. However, if the actual source is on the opposite side or both sides simultaneously, the reconstruction results will be distorted or even unable to determine the true source location. Another method is to place a large area of ​​shielding material on one side of the detector to block photons incident from the other side to prevent mirror-image interference. However, the shielding layer significantly increases the weight of the equipment, and high-energy photons may still penetrate the shielding, causing residual interference.

[0006] Therefore, it is evident that the existing Compton imaging system with planar detectors still lacks an effective and simple solution to address the uncertainty of the incident direction when achieving full-space imaging. Summary of the Invention

[0007] To address the aforementioned problems, the present invention aims to provide a single-layer Compton camera system and imaging method to achieve omnidirectional imaging of a radiation source without requiring depth information from a detector, while avoiding the generation of image artifacts.

[0008] To solve the above-mentioned technical problems, the present invention provides the following technical solution: On the one hand, a single-layer Compton camera system is provided, comprising: A single-plane pixel-type gamma-ray detector is used to collect gamma-ray interaction event data, including the time information, energy information, and two-dimensional position information of each interaction in the detector plane, and to form a pixel count distribution. A shielding structure is set on one side of the detector plane. The shielding structure is located in a local area of ​​the detector and is used to cause a local count loss feature in the pixel count distribution when gamma rays are incident from the side where the shielding structure is located. The discrimination and imaging module determines the gamma ray incident side based on the local count missing feature, and performs Compton imaging reconstruction within the corresponding hemispherical field of view according to the determined incident side to obtain the reconstructed image within the hemispherical field of view.

[0009] Optionally, the single-plane pixel-type gamma-ray detector is formed by a two-dimensional array of multiple detection units to create a detection plane; The single-plane pixel-type gamma-ray detector is either a pixelated scintillator detector array or a pixelated semiconductor detector array.

[0010] Optionally, the shielding structure is made of a material that attenuates the gamma energy region of interest, and can partially absorb and / or scatter gamma rays incident from its side and passing through the shielding structure, so that the detector area corresponding to the projection of the shielding structure forms a local count deficiency feature in the pixel count distribution, which is manifested as a low count window region.

[0011] Optionally, the shielding structure is arranged adjacent to or in contact with the detector plane; the shape of the shielding structure is any one of a block, a plate, or a strip, or a combination of the above.

[0012] Optionally, the discrimination and imaging module specifically includes: The counting matrix construction unit forms a pixel counting matrix based on the pixel count distribution of the detector. The local low count detection unit scans the pixel count matrix using a sliding window and compares the count within the sliding window with its surrounding annular neighborhood to detect whether there is a local low count region caused by an occlusion structure. The incident side hemisphere selection unit uses a threshold method to determine local low-count regions and identify the incident side; The sequence determination unit identifies the Compton scattering and absorption sites of the interactions for events involving at least two interactions. The Compton image reconstruction unit performs Compton imaging reconstruction only within the hemispherical field of view on the corresponding incident side, obtaining a reconstructed image within the hemispherical field of view.

[0013] Optionally, the determination process of the incident-side hemisphere selection unit is as follows: Define the following discriminant: Missing count ratio: Standardized residuals: in, This represents the total count within the sliding window. The number of pixels in the window. The average pixel count within the circular neighborhood; when and / or When a local low-count region is identified, and This can be a preset or adaptive threshold.

[0014] Optionally, the sequence determination unit may employ one or more combinations of energy comparison method, time order method, or probability determination method based on physical constraints.

[0015] Optionally, the Compton image reconstruction unit employs any one or more combinations of back projection, filtered back projection, statistical iterative reconstruction, algebraic reconstruction, maximum likelihood class reconstruction, or maximum a posteriori class reconstruction. The Compton scattering angle is calculated according to the Compton scattering formula. θ : in, The incident gamma ray energy or estimated energy. Energy is deposited at the scattering site. is the electron rest energy constant.

[0016] Optionally, the system further includes: The output display module is used to output and display the reconstructed image.

[0017] On the other hand, an imaging method based on the single-layer Compton camera system is provided, the method comprising: S1. Event Acquisition and Screening: Acquire gamma-ray interaction event data and screen events that meet the Compton imaging conditions; the event data includes the time information, energy information, and two-dimensional position information in the detector plane for each interaction. S2. Incident side determination: Construct a pixel counting matrix, perform local comparative analysis on the pixel counting matrix to detect local count missing features caused by occlusion structure, and determine the gamma ray incident side based on the detection results; S3. Sequence determination: Determine the order of Compton scattering sites and absorption sites for events involving at least two interactions; S4. Compton Reconstruction within the Hemispherical Field of View: Based on the incident side determination result, Compton imaging reconstruction is performed on the event data only within the hemispherical field of view of the corresponding incident side to obtain the reconstructed image within the hemispherical field of view.

[0018] The beneficial effects of the technical solution provided by this invention include at least the following: (1) Simplified structure and easy to miniaturize: The system only needs a single-plane pixel detector with a local occlusion structure to realize incident side determination and hemispherical reconstruction, without the need to add an extra detector layer or three-dimensional positioning structure, thus reducing volume and weight.

[0019] (2) Not dependent on the depth of action information: The incident prior can be obtained through the count missing features formed by the occlusion structure without the need for the detector to provide the depth of action coordinates, thereby reducing the dependence on the detector thickness design and complex readout scheme.

[0020] (3) Effective suppression of mirror artifacts: By determining the incident side before reconstruction and limiting the reconstruction to the corresponding hemispherical field of view, the artifact interference caused by the mirror solution of the other hemisphere can be eliminated, thereby improving the reliability of radiation source positioning. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a schematic diagram of the structure of a single-layer Compton camera system provided in an embodiment of the present invention; Figure 2 This is a functional module diagram of a single-layer Compton camera system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the comparison between the sliding window and the neighborhood for low count detection provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of hemispherical field of view limitation and image artifact suppression provided in an embodiment of the present invention.

[0023] Explanation of reference numerals in the attached figures: 1. Single-plane pixel gamma-ray detector; 2. Obstruction structure; 101. Pixel counting matrix; 102. Sliding window; 103. Annular neighborhood. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0025] This invention provides a single-layer Compton camera system, with reference to... Figures 1-2 As shown, the system includes: a single-plane pixel gamma-ray detector 1, a shielding structure 2 disposed on one side of the detector plane, and a discrimination and imaging module.

[0026] A single-plane pixel-type gamma-ray detector 1 is used to collect gamma-ray interaction event data, including the time and energy information of each interaction, as well as the two-dimensional position information in the detector plane, and to form a pixel count distribution.

[0027] As an optional implementation, the single-plane pixel gamma-ray detector 1 consists of a two-dimensional array of multiple detection units forming a detection plane. The single-plane pixel gamma-ray detector 1 can be any of the pixelated scintillator detector array or pixelated semiconductor detector array, or other detectors capable of outputting photon timing information, pixel energy information, and two-dimensional position information. This embodiment does not limit its materials, size, or pixel scale.

[0028] The shielding structure 2 is located in a local area of ​​the detector and covers the local area of ​​the detector. It is used to cause the pixel count distribution to produce a local count missing feature when gamma rays are incident from the side where the shielding structure 2 is located.

[0029] The shielding structure 2 is made of a material that has an attenuation effect on the gamma energy region of interest. It can partially absorb and / or scatter gamma rays that are incident from one side of the shielding structure and pass through the shielding structure 2, so that the detector area corresponding to the projection of the shielding structure forms a local count deficiency feature in the pixel count distribution, which is manifested as a low count window region.

[0030] The shielding structure 2 is arranged adjacent to or in contact with the detector plane, and its shape is any one of block, plate, strip, or a combination of the above.

[0031] The function of the shielding structure 2 is as follows: when gamma rays are incident from the side where the shielding structure 2 is located and enter the detector after passing through the shielding structure 2, the shielding structure 2 will absorb or scatter some of the gamma rays, so that the detector area corresponding to its projection will show a local count decrease "attenuation footprint" in the count distribution, which is manifested as a low count window; when gamma rays are incident from the other side of the detector plane, since they do not pass through the shielding structure 2, the above-mentioned local low count attenuation footprint is not obvious or does not appear.

[0032] The discrimination and imaging module determines the gamma ray incident side based on the local count missing feature, and performs Compton imaging reconstruction within the corresponding hemispherical field of view according to the determined incident side to obtain the reconstructed image within the hemispherical field of view.

[0033] Specifically, the discrimination and imaging module includes: a counting matrix construction unit, a local low-count detection unit, an incident side hemisphere selection unit, a sequence determination unit, and a Compton image reconstruction unit. These units can be implemented in software by the same processor / computing device, or in hardware circuitry or a combination of both; this embodiment does not limit their implementation.

[0034] To obtain prior information on the incident side, this embodiment of the invention makes a judgment based on the local count missing features formed on the count distribution by the occlusion structure 2. Figure 3 This is a schematic diagram of the comparison between the sliding window and the neighborhood for low-count detection provided in an embodiment of the present invention.

[0035] like Figure 3 As shown, the pixel counting matrix 101 is first formed by the counting matrix construction unit based on the pixel count distribution of the detector. The counting source can be selected as: photoelectric absorption event counting, full-energy event counting that meets the energy window, or Compton coincidence event counting that meets the preset screening conditions, etc., and this embodiment does not limit it.

[0036] Subsequently, the local low count detection unit scans the pixel count matrix 101 using a sliding window 102 and compares the count within the sliding window 102 with its surrounding annular neighborhood 103 to detect whether there is a local low count region caused by the occlusion structure 2.

[0037] After performing low-count window detection, the incident-side hemisphere selection unit uses a threshold method to determine the local low-count region and identify the incident side.

[0038] The determination process of the incident-side hemisphere selection unit is as follows: Define the following discriminant: Missing count ratio: Standardized residuals: in, This represents the total count within the sliding window. The number of pixels in the window. The average pixel count within the circular neighborhood; when and / or When a local low-count region is identified, and This can be a preset or adaptive threshold. Threshold and The value can be determined through offline calibration, parameter search, or adaptive statistical methods. This embodiment does not limit the specific value or determination method.

[0039] The incident-side hemisphere selection unit outputs an incident-side determination based on the detection results: if a local low-count region is detected, the gamma rays are determined to originate from the side where the occluding structure 2 is located; if no local low-count region is detected, the gamma rays are determined to originate from the opposite side of the occluding structure 2. This determination serves as a priori constraint for subsequent image reconstruction, used to select the corresponding hemisphere field of view and suppress mirror solutions.

[0040] Before performing Compton imaging reconstruction, detector events can be screened and sequenced to increase the proportion of valid events and reduce the impact of erroneous sequences on reconstruction.

[0041] The detector event screening includes selecting events that satisfy the Compton imaging constraints from multiple interaction events collected by the detector. For example, in scenarios where the incident gamma characteristic energy is known or can be estimated, an energy window can be set to screen events whose total energy falls within the energy window; physical constraints such as scattering angle and energy deposition range can also be set to eliminate unreasonable events. This embodiment does not limit the specific form of the screening conditions.

[0042] For events involving at least two interactions, the sequence determination unit identifies the Compton scattering and absorption sites of the interactions, i.e., which interaction is the Compton scattering site and which is the absorption site. The sequence determination unit employs any one or a combination of energy comparison, time ordering, or probabilistic determination methods based on physical constraints. This embodiment does not limit the specific implementation method.

[0043] After obtaining the incident side determination result, the Compton image reconstruction unit performs Compton imaging reconstruction only within the hemispherical field of view of the corresponding incident side, and obtains the reconstructed image within the hemispherical field of view, thereby avoiding interference from the mirror solution of the other hemisphere.

[0044] As an alternative implementation, the Compton scattering angle can be calculated first using the Compton scattering formula. θ : in, The incident gamma ray energy or estimated energy. Energy is deposited at the scattering site. is the electron rest energy constant.

[0045] The initial image distribution can then be formed by Compton conic backprojection, and further optimized by an algorithm. The algorithm can be any one or a combination of backprojection, filtered backprojection, statistical iterative reconstruction, algebraic reconstruction, maximum likelihood class reconstruction, or maximum a posteriori class reconstruction. This embodiment does not limit the specific algorithm type.

[0046] Furthermore, the system also includes an output display module for outputting and displaying the reconstructed image.

[0047] Figure 4 This is a schematic diagram illustrating hemispherical field-of-view limitation and image artifact suppression provided in an embodiment of the present invention. Figure 4 As shown, to intuitively illustrate the effect of incident-side prior on suppressing mirror artifacts, an embodiment of the present invention provides a display method: when no incident-side prior is introduced or the hemispherical field of view is not restricted, the reconstruction result may simultaneously show the real source and artifacts that are mirror-symmetric about the detector plane; however, in the process of the present invention, only the incident-side hemispherical result is output based on the incident-side determination result, thereby obtaining a reconstructed image that only contains the incident-side hemispherical field of view, and the mirror artifacts are reduced or eliminated.

[0048] Accordingly, embodiments of the present invention also provide an imaging method based on the single-layer Compton camera system, the method comprising: S1. Event Acquisition and Screening: Acquire gamma-ray interaction event data and screen events that meet the Compton imaging conditions; the event data includes the time information, energy information, and two-dimensional position information in the detector plane for each interaction. S2. Incident side determination: Construct a pixel counting matrix, perform local comparative analysis on the pixel counting matrix to detect local count missing features caused by occlusion structure, and determine the gamma ray incident side based on the detection results; If a local low-count region is detected, the gamma rays are determined to have occurred from the side where the shielding structure is located; if no local low-count region is detected, the gamma rays are determined to have occurred from the opposite side of the shielding structure.

[0049] S3. Sequence determination: Determine the order of Compton scattering sites and absorption sites for events involving at least two interactions; S4. Compton Reconstruction within the Hemispherical Field of View: Based on the incident side determination result, Compton imaging reconstruction is performed on the event data only within the hemispherical field of view of the corresponding incident side to obtain the reconstructed image within the hemispherical field of view.

[0050] The method in this embodiment is based on Figures 1-2 The technical solution of the system embodiment shown is similar in principle and effect, and will not be described again here. Through the above process, the present invention uses "incident side determination" as a priori constraint for Compton reconstruction, so that each reconstruction is only performed within the hemispherical field of view on the true incident side, thereby obtaining zonal omnidirectional capability and suppressing image artifacts.

[0051] Compared with existing technologies, this invention effectively solves the mirror effect problem that occurs when the Compton camera of the planar detector performs omnidirectional imaging without working depth information. It can achieve zonal omnidirectional radiation source localization without adding an extra detector layer or complex readout circuit, and has the advantages of compact structure and simple hardware implementation.

[0052] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Unless otherwise specified, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0053] The use of terms such as "an embodiment," "an embodiment," "an exemplary embodiment," and "some embodiments" in the specification indicates that the described embodiment may include a specific feature, structure, or characteristic, but not every embodiment necessarily includes that specific feature, structure, or characteristic. Furthermore, when a specific feature, structure, or characteristic is described in connection with an embodiment, implementing such a feature, structure, or characteristic in conjunction with other embodiments (whether explicitly described or not) should be within the knowledge of those skilled in the art.

[0054] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0055] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0056] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0057] In the embodiments provided by this invention, it should be understood that the disclosed devices, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another device, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0058] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0059] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0060] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0061] This invention encompasses any substitutions, modifications, equivalent methods, and solutions made within the spirit and scope of this invention. To provide the public with a thorough understanding of this invention, specific details are described in detail in the following preferred embodiments; however, those skilled in the art will fully understand the invention even without these details. Furthermore, to avoid unnecessary misunderstanding of the essence of this invention, well-known methods, processes, procedures, components, and circuits are not described in detail.

[0062] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A single-layer Compton camera system, characterized in that, include: A single-plane pixel-type gamma-ray detector is used to collect gamma-ray interaction event data, including the time information, energy information, and two-dimensional position information of each interaction in the detector plane, and to form a pixel count distribution. A shielding structure is set on one side of the detector plane. The shielding structure is located in a local area of ​​the detector and is used to cause a local count loss feature in the pixel count distribution when gamma rays are incident from the side where the shielding structure is located. The discrimination and imaging module determines the gamma ray incident side based on the local count missing feature, and performs Compton imaging reconstruction within the corresponding hemispherical field of view according to the determined incident side to obtain the reconstructed image within the hemispherical field of view.

2. The single-layer Compton camera system according to claim 1, characterized in that, The single-plane pixel-type gamma-ray detector consists of a two-dimensional array of multiple detection units forming a detection plane. The single-plane pixel-type gamma-ray detector is either a pixelated scintillator detector array or a pixelated semiconductor detector array.

3. The single-layer Compton camera system according to claim 1, characterized in that, The shielding structure is made of a material that attenuates the gamma energy region of interest. It can partially absorb and / or scatter gamma rays that are incident from one side of the shielding structure and pass through it, so that the detector area corresponding to the projection of the shielding structure forms a local count deficiency feature in the pixel count distribution, which is manifested as a low count window region.

4. The single-layer Compton camera system according to claim 1, characterized in that, The shielding structure is arranged adjacent to or in contact with the detector plane; the shape of the shielding structure is any one of the following: block, plate, strip, or a combination of the above.

5. The single-layer Compton camera system according to claim 1, characterized in that, The discrimination and imaging module specifically includes: The counting matrix construction unit forms a pixel counting matrix based on the pixel count distribution of the detector. The local low count detection unit scans the pixel count matrix using a sliding window and compares the count within the sliding window with its surrounding annular neighborhood to detect whether there is a local low count region caused by an occlusion structure. The incident side hemisphere selection unit uses a threshold method to determine local low-count regions and identify the incident side; The sequence determination unit identifies the Compton scattering and absorption sites of the interactions for events involving at least two interactions. The Compton image reconstruction unit performs Compton imaging reconstruction only within the hemispherical field of view on the corresponding incident side, obtaining a reconstructed image within the hemispherical field of view.

6. The single-layer Compton camera system according to claim 5, characterized in that, The determination process of the incident-side hemisphere selection unit is as follows: Define the following discriminant: Missing count ratio: Standardized residuals: in, This represents the total count within the sliding window. The number of pixels in the window. The average pixel count within the circular neighborhood; when and / or When a local low-count region is identified, and This can be a preset or adaptive threshold.

7. The single-layer Compton camera system according to claim 5, characterized in that, The sequence determination unit employs any one or a combination of energy comparison method, time sequence method, or probability determination method based on physical constraints.

8. The single-layer Compton camera system according to claim 5, characterized in that, The Compton image reconstruction unit employs any one or more combinations of back projection, filtered back projection, statistical iterative reconstruction, algebraic reconstruction, maximum likelihood class reconstruction, or maximum a posteriori class reconstruction. The Compton scattering angle is calculated according to the Compton scattering formula. θ : in, The incident gamma ray energy or estimated energy. Energy is deposited at the scattering site. is the electron rest energy constant.

9. The single-layer Compton camera system according to claim 1, characterized in that, The system also includes: The output display module is used to output and display the reconstructed image.

10. An imaging method based on a single-layer Compton camera system according to any one of claims 1-9, characterized in that, The method includes: S1. Event Acquisition and Screening: Acquire gamma-ray interaction event data and screen events that meet the Compton imaging conditions; the event data includes the time information, energy information, and two-dimensional position information in the detector plane for each interaction. S2. Incident side determination: Construct a pixel counting matrix, perform local comparative analysis on the pixel counting matrix to detect local count missing features caused by occlusion structure, and determine the gamma ray incident side based on the detection results; S3. Sequence determination: Determine the order of Compton scattering sites and absorption sites for events involving at least two interactions; S4. Compton Reconstruction within the Hemispherical Field of View: Based on the incident side determination result, Compton imaging reconstruction is performed on the event data only within the hemispherical field of view of the corresponding incident side to obtain the reconstructed image within the hemispherical field of view.

Images