Multi-mode iterative reconstruction method and device

Abstract

The invention provides a multimode iterative reconstruction method and device, and relates to the technical field of nuclear radiation detection. The method comprises the following steps: acquiring event information of interaction between gamma photons and a three-dimensional position sensitive semiconductor detection unit in a panoramic gamma camera system; based on the prior energy, the Compton scattering event count in the event information and the photoelectric absorption event count in the event information, obtaining an information amount, and calculating a weight according to the information amount; compton sequence reconstruction is carried out based on prior energy, and a multimode system transmission matrix is constructed according to the reconstructed Compton sequence; and performing multi-mode iteration reconstruction based on the weight and the multi-mode system transmission matrix, outputting a stable high signal-to-noise ratio image, and determining the spatial distribution of the radioactive source. According to the multi-mode iteration reconstruction method based on the coding aperture combined with the Compton and non-collimation technology, the problems that in traditional multi-mode gamma imaging, the reconstruction resolution ratio is poor, and the imaging signal-to-noise ratio is unstable are solved, and the imaging energy range, the imaging view field and the resolution ratio are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of nuclear radiation detection, and in particular to a multi-mode iterative reconstruction method and device. Background Art

[0002] Nuclear safety is a critical area for ensuring the safe use of nuclear energy, preventing the misuse of radioactive materials, and protecting the public and the environment from radiation hazards. Gamma-ray imaging technology can accurately locate radiation sources, enabling visual monitoring of radiation exposure. It also offers excellent response time and detection efficiency, effectively reducing risk factors and is currently widely used in nuclear safety monitoring.

[0003] In recent years, multimodal imaging techniques based on coded aperture imaging and Compton imaging have gradually gained attention within the field due to their ability to increase the amount of photon information obtained, expand the imaging energy range, enhance the image signal-to-noise ratio, reduce reconstruction uncertainty, and ensure detection efficiency. However, existing multimodal image reconstruction algorithms have not yet explored the trade-offs between the various modal terms in the probability density function of the projection data. As a result, the shortcomings of each mode easily affect each other, and the advantages of each mode are difficult to fully utilize. As a result, the overall resolution and signal-to-noise ratio of the final multimodal reconstructed image are, in some cases, even inferior to those of a single-mode reconstruction image. Summary of the Invention

[0004] In order to solve the technical problems of poor reconstruction resolution and unstable imaging signal-to-noise ratio in traditional multi-mode gamma imaging, the embodiments of the present invention provide a multi-mode iterative reconstruction method and device. The technical solution is as follows:

[0005] In one aspect, a multi-mode iterative reconstruction method is provided. The method is implemented by a multi-mode iterative reconstruction device, and the method includes: S1. Acquire event information of gamma photons interacting with three-dimensional position-sensitive semiconductor detection units in a panoramic gamma camera system.

[0006] S2. Obtain information based on the prior energy, the Compton scattering event count in the event information, and the photoelectric absorption event count in the event information, and calculate the weight according to the information; reconstruct the Compton sequence based on the prior energy, and construct the multimode system transmission matrix according to the reconstructed Compton sequence.

[0007] S3. Perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix to output a stable high signal-to-noise ratio image and determine the spatial distribution of the radiation source.

[0008] Optionally, the event information in S1 includes: timestamp, energy, three-dimensional position coordinates, action sequence and action type.

[0009] Among them, the action types include: Compton scattering events and photoelectric absorption events.

[0010] Timestamp, recorded by triggering the time of the signal pulse captured by the data acquisition system within the panoramic gamma camera system.

[0011] Energy, determined by the amplitude of the signal pulse.

[0012] The three-dimensional position coordinates are determined by the anode response pixel position of the detector array to determine the two-dimensional lateral spatial coordinates of the photon action event, and the action depth of the photon action event is determined by analyzing the ratio of the cathode and anode signal amplitudes. The three-dimensional position coordinates are determined based on the two-dimensional lateral spatial coordinates and the action depth.

[0013] The action sequence is determined by measuring the electron drift time and analyzing the timing information of the pulses corresponding to each interaction point.

[0014] The type of interaction is determined by the number of interaction points and the energy deposition pattern at each point combined with the position information.

[0015] Optionally, the calculation weight in S2 is as shown in the following formula (1): (1) Where, is the weight, is the optimization degree factor, is the prior energy of the radiation source, is the total number of Compton scattering events detected by the detector, It is the total number of photoelectric absorption events detected by the detector.

[0016] Optionally, the Compton sequence reconstruction in S2 includes: The interaction sequence in the full-energy double Compton coincidence event is determined by the magnitude of the deposited energy, and a Compton edge test is performed.

[0017] Among them, the calculation formula of Compton edge test is as shown in the following formula (2): (2) Where, For Compton Edge Energy, is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0018] Optionally, the multi-mode system transmission matrix in S2 includes: a non-collimation-mechanical collimation mode system transmission matrix and a Compton mode system transmission matrix.

[0019] Among them, the transmission matrix of the non-collimation-mechanical collimation mode system is obtained by analytical calculation method, as shown in the following formula (3): (3) Where, is the transmission matrix of the non-collimation-mechanical collimation mode system, is the detector voxel, is the image plane pixel, is the attenuation coefficient of the high-density alloy, is the slave pixel intercepted by the mechanical collimator To detector voxel The radiation path, is the attenuation coefficient of the semiconductor detector, is the slave pixel intercepted by the detector To detector voxel The radiation path of the surface, is the number of slave pixels intercepted by the detector voxel To detector voxel Radiating paths from the center.

[0020] The Compton mode system transfer matrix is ​​obtained by analytical calculation method, as shown in the following equation (4): (4) Where, is the transmission matrix of the Compton mode system, For Compton to meet the sequence of events, For the The number of pixels intercepted by the detector in the action sequence The radiation path to the Compton scattering site, for The Compton differential cross section, is the Compton scattering angle, For the The radiation path from the Compton scattering action position to the photoelectric absorption action position intercepted by the detector in a sequence of actions.

[0021] The calculation formula of Compton differential cross section is shown in the following formula (5): (5) Where, , is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0022] Optionally, multi-mode iterative reconstruction is performed based on the weights and the multi-mode system transmission matrix in S3, as shown in the following equation (6): (6) Where, for The new estimate after iterations, for The current estimate after iterations, is the image plane pixel, is the weight, For the total number of Compton-compliant events, For the The count of Compton measurements in the action sequence, is the transmission matrix of the Compton mode system, is the total number of pixels in the image space, for The normalized summation process of the first iteration The current estimated value of image pixels, is the image pixel index, is the total number of detector voxels, is the detector voxel The photon measurement count at is the transmission matrix of the non-collimation-mechanical collimation mode system, is the sensitivity matrix.

[0023] Optionally, the panoramic gamma camera system includes: a three-dimensional position-sensitive semiconductor detection unit and a coding plate module without a shielding layer.

[0024] Among them, the three-dimensional position sensitive semiconductor detection unit includes: a three-dimensional position sensitive semiconductor, a dedicated integrated circuit chip, a field programmable logic gate array and a data acquisition system.

[0025] The coding plate module without a shielding layer includes: a coding plate and a side support layer.

[0026] On the other hand, a multi-mode iterative reconstruction device is provided, which is applied to the multi-mode iterative reconstruction method, and the device includes: The acquisition module is used to obtain event information of gamma photons interacting with three-dimensional position-sensitive semiconductor detection units in a panoramic gamma camera system.

[0027] The construction module is used to obtain information based on prior energy, Compton scattering event counts in event information, and photoelectric absorption event counts in event information, and calculate weights based on the information; reconstruct the Compton sequence based on the prior energy, and construct a multi-mode system transmission matrix based on the reconstructed Compton sequence.

[0028] The output module is used to perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix, output stable high signal-to-noise ratio images, and determine the spatial distribution of radiation sources.

[0029] Optionally, the event information includes: timestamp, energy, three-dimensional position coordinates, action sequence and action type.

[0030] Among them, the action types include: Compton scattering events and photoelectric absorption events.

[0031] Timestamp, recorded by triggering the time of the signal pulse captured by the data acquisition system within the panoramic gamma camera system.

[0032] Energy, determined by the amplitude of the signal pulse.

[0033] The three-dimensional position coordinates are determined by the anode response pixel position of the detector array to determine the two-dimensional lateral spatial coordinates of the photon action event, and the action depth of the photon action event is determined by analyzing the ratio of the cathode and anode signal amplitudes. The three-dimensional position coordinates are determined based on the two-dimensional lateral spatial coordinates and the action depth.

[0034] The action sequence is determined by measuring the electron drift time and analyzing the timing information of the pulses corresponding to each interaction point.

[0035] The type of interaction is determined by the number of interaction points and the energy deposition pattern at each point combined with the position information.

[0036] Optionally, the weight is calculated as shown in the following formula (1): (1) Where, is the weight, is the optimization degree factor, is the prior energy of the radiation source, is the total number of Compton scattering events detected by the detector, It is the total number of photoelectric absorption events detected by the detector.

[0037] Optionally, Compton sequence reconstruction, including: The interaction sequence in the full-energy double Compton coincidence event is determined by the magnitude of the deposited energy, and a Compton edge test is performed.

[0038] Among them, the calculation formula of Compton edge test is as shown in the following formula (2): (2) Where, For Compton Edge Energy, is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0039] Optionally, the multi-mode system transmission matrix includes: a non-collimation-mechanical collimation mode system transmission matrix and a Compton mode system transmission matrix.

[0040] Among them, the transmission matrix of the non-collimation-mechanical collimation mode system is obtained by analytical calculation method, as shown in the following formula (3): (3) Where, is the transmission matrix of the non-collimation-mechanical collimation mode system, is the detector voxel, is the image plane pixel, is the attenuation coefficient of the high-density alloy, is the slave pixel intercepted by the mechanical collimator To detector voxel The radiation path, is the attenuation coefficient of the semiconductor detector, is the slave pixel intercepted by the detector To detector voxel The radiation path of the surface, is the number of slave pixels intercepted by the detector voxel To detector voxel Radiating paths from the center.

[0041] The Compton mode system transfer matrix is ​​obtained by analytical calculation method, as shown in the following equation (4): (4) Where, is the transmission matrix of the Compton mode system, For Compton to meet the sequence of events, For the The number of pixels intercepted by the detector in the action sequence The radiation path to the Compton scattering site, for The Compton differential cross section, is the Compton scattering angle, For the The radiation path from the Compton scattering action position to the photoelectric absorption action position intercepted by the detector in a sequence of actions.

[0042] The calculation formula of Compton differential cross section is shown in the following formula (5): (5) Where, , is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0043] Optionally, multi-mode iterative reconstruction is performed based on the weights and the multi-mode system transmission matrix, as shown in the following equation (6): (6) Where, for The new estimate after iterations, for The current estimate after iterations, is the image plane pixel, is the weight, For the total number of Compton-compliant events, For the The count of Compton measurements in the action sequence, is the transmission matrix of the Compton mode system, is the total number of pixels in the image space, for The normalized summation process of the first iteration The current estimated value of image pixels, is the image pixel index, is the total number of detector voxels, is the detector voxel The photon measurement count at is the transmission matrix of the non-collimation-mechanical collimation mode system, is the sensitivity matrix.

[0044] Optionally, the panoramic gamma camera system includes: a three-dimensional position-sensitive semiconductor detection unit and a coding plate module without a shielding layer.

[0045] Among them, the three-dimensional position sensitive semiconductor detection unit includes: a three-dimensional position sensitive semiconductor, a dedicated integrated circuit chip, a field programmable logic gate array and a data acquisition system.

[0046] The coding plate module without a shielding layer includes: a coding plate and a side support layer.

[0047] On the other hand, a multi-mode iterative reconstruction device is provided, which includes: a processor; a memory, wherein computer-readable instructions are stored in the memory, and when the computer-readable instructions are executed by the processor, any one of the multi-mode iterative reconstruction methods described above is implemented.

[0048] On the other hand, a computer-readable storage medium is provided, wherein the storage medium stores at least one instruction, and the at least one instruction is loaded and executed by a processor to implement any one of the above-mentioned multi-mode iterative reconstruction methods.

[0049] The beneficial effects brought about by the technical solution provided by the embodiment of the present invention include at least: In this paper, addressing the problem that existing multimodal image reconstruction algorithms have not yet explored the trade-offs between the various modal terms in the probability density function of projection data, resulting in the final multimodal reconstructed image resolution being inferior to that of single-mode reconstruction in some cases, the present invention provides a weighted multimodal iterative reconstruction method. This method combines the Compton collimation method with the collimation-free mechanical collimation method, analytically calculates the three-mode system matrix, and incorporates information about the radiation source energy prior and the ratio of Compton scattering event counts to photoelectric absorption event counts. Multimodal iterative reconstruction is then performed based on the weights, achieving stable multimodal imaging with a higher weighting of Compton imaging results for high-energy bands and a higher weighting of collimation-free mechanical collimation results for medium and low-energy bands. This method overcomes the problems of conventional iterative reconstruction algorithms, such as their inability to achieve targeted high-resolution imaging based on radiation source characteristics, low efficiency and sensitivity, and unstable imaging results, effectively improving the imaging energy range, field of view, and resolution of multimodal gamma cameras. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0051] Figure 1 This is a flow chart of a multi-mode iterative reconstruction method provided by an embodiment of the present invention; Figure 2 Schematic diagram of a multi-mode panoramic gamma camera system and the field of view of each mode provided by an embodiment of the present invention; Figure 3 is a schematic diagram of a three-dimensional position-sensitive semiconductor detection unit provided by an embodiment of the present invention; Figure 4 This is a block diagram of a multi-mode iterative reconstruction device provided by an embodiment of the present invention; Figure 5 1 is a schematic structural diagram of a multi-mode iterative reconstruction device provided by an embodiment of the present invention; Figure numerals: 1. Full decoding field of view of coded aperture imaging mode; 2. Half decoding field of view of coded aperture imaging mode; 3. Field of view of non-collimated imaging mode; 4. Field of view of Compton imaging mode; 11. Coding plate; 12. Side support layer; 13. Three-dimensional position-sensitive semiconductor detection unit; 14. Electronics system; 111. Semiconductor detection module; 112. Pixel-type anode; 113. Flat cathode; 114. Compton scattering event in the three-dimensional depth of action space corresponding to a planar pixel unit; 115. Photoelectric absorption event in the three-dimensional depth of action space corresponding to a planar pixel unit. DETAILED DESCRIPTION

[0052] The technical solution of the present invention is described below in conjunction with the accompanying drawings.

[0053] In the embodiments of the present invention, words such as "exemplarily" and "for example" are used to indicate examples, illustrations, or explanations. Any embodiment or design described as an "exemplary" in the present invention should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of the word "exemplary" is intended to present concepts in a concrete manner. Furthermore, in the embodiments of the present invention, "and / or" can mean both or either of the two.

[0054] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that, when the distinction is not emphasized, the meanings they convey are the same. The terms "of," "corresponding," and "corresponding" may sometimes be used interchangeably. It should be noted that, when the distinction is not emphasized, the meanings they convey are the same.

[0055] In the embodiments of the present invention, sometimes a subscript such as W1 may be written as a non-subscript such as W1. When the difference is not emphasized, the meanings to be expressed are the same.

[0056] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0057] The embodiment of the present invention provides a multi-mode iterative reconstruction method, which can be implemented by a multi-mode iterative reconstruction device, which can be a terminal or a server. Figure 1 The multi-mode iterative reconstruction method flow chart shown in FIG. 1 may include the following steps:

[0058] S1. Acquire event information of gamma photons interacting with three-dimensional position-sensitive semiconductor detection units in a panoramic gamma camera system.

[0059] In one feasible implementation, event information of gamma photons interacting with detection units within a panoramic gamma camera system is obtained, including timestamp, energy, three-dimensional position coordinates, interaction sequence, and interaction type. The interaction types include Compton scattering events and photoelectric absorption events.

[0060] Specifically, the time of triggering the signal pulse captured by the high-speed data acquisition system is recorded as a timestamp; The energy is determined by the amplitude of the signal pulse; The two-dimensional lateral spatial coordinates of the photon action event are determined by the grid-like anode response pixel positions of the detector array; The depth of photon impact events is determined by analyzing the ratio of cathode and anode signal amplitudes; The action sequence is determined by analyzing the timing information of the pulses corresponding to each interaction point by measuring the electron drift time; Determining the type of interaction based on the number of interaction points and the energy deposition pattern of each point in combination with position information, wherein the interaction type includes one of a Compton scattering event and a photoelectric absorption event; The gamma photon event information is obtained based on the timestamp, energy, two-dimensional transverse space coordinates, action depth, action sequence, and action type of the gamma photon action event.

[0061] S2. Obtain information based on the prior energy, the Compton scattering event count in the event information, and the photoelectric absorption event count in the event information, and calculate the weight according to the information; reconstruct the Compton sequence based on the prior energy, and construct the multimode system transmission matrix according to the reconstructed Compton sequence.

[0062] In a feasible implementation, information is obtained based on prior energy, Compton scattering events, and photoelectric absorption event counts to calculate weights, and Compton sequence reconstruction is performed simultaneously to construct a multi-mode system transmission matrix.

[0063] Optionally, a weight calculation method based on the amount of information is: (1) Where, is the weight, is the optimization degree factor, is the prior energy of the radioactive source, which is obtained based on the existing nuclide identification technology. is the total number of Compton scattering events detected by the detector, It is the total number of photoelectric absorption events detected by the detector.

[0064] Optionally, the above The calculation method of the value is any one of random search, Bayesian optimization, evolutionary algorithm, gradient descent algorithm, and deep learning algorithm. Specifically, this embodiment adopts the random search method. Of course, it is understandable that this embodiment is not limited to Selection of value calculation method.

[0065] Optionally, the Compton sequence reconstruction method is: The interaction sequence in the full-energy double Compton coincidence event is determined by the amount of deposited energy, and a Compton edge test is performed. The Compton edge energy is used to screen for correct double Compton coincidence events. Only coincidence events within the edge energy range are reconstructed. Therefore, edge computing serves as a conditional judgment for whether to proceed with sequence reconstruction.

[0066] Among them, the Compton edge calculation formula is: (2) Where, For Compton Edge Energy, is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0067] Optionally, the multi-mode system transmission matrix in S2 includes: a non-collimated-mechanical collimation mode system transmission matrix and a Compton mode system transmission matrix. The coded aperture mode is a type of mechanical collimation mode.

[0068] Among them, the system matrix calculation method includes: The transfer matrix of the non-collimation-mechanical collimation mode system is obtained by analytical calculation method. The analytical calculation formula of the transfer matrix of the non-collimation-mechanical collimation mode system is: (3) Where, is the transmission matrix of the non-collimation-mechanical collimation mode system, is the detector voxel, is the image plane pixel, is the attenuation coefficient of the high-density alloy, is the slave pixel intercepted by the mechanical collimator To detector voxel The radiation path, is the attenuation coefficient of the semiconductor detector, is the slave pixel intercepted by the detector To detector voxel The radiation path of the surface, is the number of slave pixels intercepted by the detector voxel To detector voxel Radiating paths from the center.

[0069] The Compton mode system transfer matrix is ​​obtained by analytical calculation method. The analytical calculation formula of the Compton mode system transfer matrix is: (4) Where, is the transmission matrix of the Compton mode system, For Compton to meet the sequence of events, For the The number of pixels intercepted by the detector in the action sequence The radiation path to the Compton scattering site, for The Compton differential cross section, is the Compton scattering angle, For the The radiation path from the Compton scattering action position to the photoelectric absorption action position intercepted by the detector in a sequence of actions.

[0070] The calculation formula of Compton differential cross section is: (5) Where, , is the prior energy of the radiation source, is the electron rest mass, The speed of light.

[0071] S3. Perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix to output a stable high signal-to-noise ratio image and determine the spatial distribution of the radiation source.

[0072] In one feasible embodiment, the Compton, uncollimated, and coded aperture imaging modes are integrated to perform multi-mode iterative reconstruction based on weights, outputting stable high signal-to-noise ratio images within a 4π range, wherein high angular resolution images are obtained within the mechanical collimation field of view, thereby determining the spatial distribution of the radiation source.

[0073] Furthermore, the acquired list mode data and information required for multimodal image reconstruction are used for iterative reconstruction of the list mode maximum likelihood expectation maximization algorithm. The present invention innovatively introduces the amount of information according to the characteristics of each mode and derives the weighted multimodal iterative image reconstruction formula as follows: (6) Where, for The new estimate after iterations, for The current estimate after iterations, is the image plane pixel, is the weight, For the total number of Compton-compliant events, For the The count of Compton measurements in the action sequence, is the transmission matrix of the Compton mode system, is the total number of pixels in the image space, for The normalized summation process of the first iteration The current estimated value of image pixels, is the image pixel index, is the total number of detector voxels, is the detector voxel The photon measurement count at is the transmission matrix of the non-collimation-mechanical collimation mode system, is the sensitivity matrix.

[0074] Optionally, the panoramic gamma camera system includes: a three-dimensional position-sensitive semiconductor detection unit and a coding plate module without a shielding layer.

[0075] Among them, the three-dimensional position sensitive semiconductor detection unit includes: a three-dimensional position sensitive semiconductor, a dedicated integrated circuit chip, a field programmable logic gate array and a data acquisition system.

[0076] The coding plate module without a shielding layer includes: a coding plate and a side support layer.

[0077] The encoding mode of the encoding board is any one of a random array, a non-redundant array, a uniform redundant array and a modified uniform redundant array.

[0078] The side support layer is a rectangular parallelepiped structure with a preset thickness, and is made of a material with a weak gamma ray blocking ability.

[0079] In a feasible implementation, Figure 2 As shown, the field of view of the multi-mode gamma camera system includes: a fully decoded field of view 1 in the coded aperture imaging mode, a semi-decoded field of view 2 in the coded aperture imaging mode, a field of view 3 in the non-collimated imaging mode, and a field of view 4 in the Compton imaging mode.

[0080] Among them, the coded aperture imaging mode full decoding field of view 1 and the coded aperture imaging mode half decoding field of view 2 constitute a high-resolution small imaging field of view; The field of view 3 of the non-collimated imaging mode is a large field of view with general resolution; The Compton imaging mode field of view 4 is a panoramic field of view of the 4π image space.

[0081] Furthermore, the coded aperture imaging mode full decoding field of view 1, the coded aperture imaging mode half decoding field of view 2, the uncollimated imaging mode field of view 3, and the Compton imaging mode field of view 4 together constitute a 4π panoramic field of view of the multi-mode gamma camera system.

[0082] Furthermore, the multi-mode gamma camera system module includes: a coding plate 11 , a side support layer 12 , a three-dimensional position-sensitive semiconductor detection unit 13 , and an electronics system 14 .

[0083] Among them, the coding plate 11 is a high-density alloy; The side support layer 12 is a rectangular structure with a preset thickness and is made of a material with a weak gamma ray blocking ability. Specifically, the side support layer 12 in this embodiment is a lightweight acrylic material with a thickness of 5 mm. The electronics system 14 includes an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and a data acquisition system (DAQ).

[0084] Optionally, the encoding scheme of the encoding plate 11 is any one of random arrays (NA), non-redundant arrays (NRA), uniformly redundant arrays (URA), and modified uniformly redundant arrays (MURA). Specifically, the encoding plate 11 of this embodiment utilizes a 13-order modified uniformly redundant array with a 2*2 nested loop structure made of tungsten alloy. It is understood that this embodiment does not limit the size, high-density alloy material, or encoding scheme of the encoding plate 11.

[0085] Optionally, the semiconductor type of the three-dimensional position-sensitive semiconductor detection unit 13 is any one of high-purity germanium (HPGe), silicon (Si), cadmium telluride (CdTe), cadmium zinc telluride (CZT), mercury iodide (HgI2), and gallium arsenide (GaAs). Specifically, the three-dimensional position-sensitive semiconductor detection unit 13 of this embodiment uses CdZnTe as the semiconductor detection crystal. Of course, it is understood that this embodiment does not limit the semiconductor type of the three-dimensional position-sensitive semiconductor detection unit 13.

[0086] Optionally, the arrangement type of the three-dimensional position-sensitive semiconductor detection units 13 is either a single probe or an array. Specifically, the three-dimensional position-sensitive semiconductor detection units 13 of this embodiment are arranged in a 2*2 array. Of course, it is understood that this embodiment does not limit the unit volume and arrangement type of the three-dimensional position-sensitive semiconductor detection units 13.

[0087] like Figure 3As shown, the three-dimensional position-sensitive semiconductor detection unit comprises: a semiconductor detection module 111 , a pixel-type anode 112 , and a flat cathode 113 .

[0088] The pixel-type anode 112 is used to collect electron-hole pairs that move toward the electrode under the action of the electric field, so as to determine the two-dimensional lateral coordinates of the interaction generated when the gamma photons interact in the semiconductor detection module 111; The flat cathode 113 is used to provide a change in the pulse signal to measure the time required for electrons to drift from the interaction point to the anode, thereby determining the depth of action.

[0089] Furthermore, the gamma photon action types that can be detected in the semiconductor detection module 111 include: Compton scattering action events 114 in the three-dimensional action depth space corresponding to a planar pixel unit, and photoelectric absorption action events 115 in the three-dimensional action depth space corresponding to a planar pixel unit.

[0090] Through the above detailed explanation of the multi-mode iterative image reconstruction method, the rapid system matrix solution of the multi-mode panoramic gamma camera system and the stable high signal-to-noise ratio iterative reconstruction of wide-energy gamma rays in the 4π imaging plane are achieved, and high-angular resolution images are obtained within the mechanical collimation field of view.

[0091] Among them, it should be noted that the sensitivity matrix acquisition method of the present invention can be any one of the analytical calculation method, the Monte Carlo simulation method, and the experimental measurement method; the preliminary estimate value in the multi-mode iterative reconstruction algorithm can be any one of the random number, direct back projection, and filtered back projection results; the distance between the image space and the center position of the detector, the image space pixel size, the detector space voxel size, the energy window threshold for screening full-energy Compton coincidence events, the number of valid Compton sequences, the iteration step size, the number of iterations, the interpolation method of image visualization, etc. can be flexibly adjusted according to actual needs.

[0092] Based on the multi-mode iterative image reconstruction method proposed in the present invention, in addition to the above advantages, the present invention is applicable to multiple fields such as nuclear safety and environmental monitoring, nuclear facility decommissioning, and nuclear medicine imaging because it can perform stable high signal-to-noise ratio imaging of far-field radiation sources within a panoramic range.

[0093] In an embodiment of the present invention, to address the problem that existing multimodal image reconstruction algorithms have not yet explored the trade-offs between the various modal terms in the probability density function of projection data, resulting in the resolution of the final multimodal reconstructed image being inferior to that of a single-mode reconstruction image in some cases, the present invention provides a weighted multimodal iterative reconstruction method. This method combines the Compton collimation method with the collimation-free mechanical collimation method, analytically calculates the three-mode system matrix, and incorporates information about the radiation source energy prior and the ratio of Compton scattering event counts to photoelectric absorption event counts. Multimodal iterative reconstruction is then performed based on the weights, achieving stable multimodal imaging with a higher weighting of Compton imaging results for high-energy bands and a higher weighting of collimation-free mechanical collimation results for medium and low-energy bands. This method overcomes the problems of conventional iterative reconstruction algorithms, such as their inability to achieve targeted high-resolution imaging based on radiation source characteristics, low efficiency and sensitivity, and unstable imaging results, effectively improving the imaging energy range, field of view, and resolution of multimodal gamma cameras.

[0094] Figure 4 FIG1 is a block diagram of a multi-mode iterative reconstruction device according to an exemplary embodiment, wherein the device is used in a multi-mode iterative reconstruction method. Figure 4 The device includes an acquisition module 310, a construction module 320, and an output module 330.

[0095] The acquisition module 310 is used to acquire event information of gamma photons interacting with three-dimensional position-sensitive semiconductor detection units in the panoramic gamma camera system.

[0096] Construction module 320 is used to obtain information based on the prior energy, the Compton scattering event count in the event information, and the photoelectric absorption event count in the event information, and calculate the weight based on the information; reconstruct the Compton sequence based on the prior energy, and construct the multimode system transmission matrix based on the reconstructed Compton sequence.

[0097] The output module 330 is used to perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix, output a stable high signal-to-noise ratio image, and determine the spatial distribution of the radiation source.

[0098] In an embodiment of the present invention, to address the problem that existing multimodal image reconstruction algorithms have not yet explored the trade-offs between the various modal terms in the probability density function of projection data, resulting in the resolution of the final multimodal reconstructed image being inferior to that of a single-mode reconstruction image in some cases, the present invention provides a weighted multimodal iterative reconstruction method. This method combines the Compton collimation method with the collimation-free mechanical collimation method, analytically calculates the three-mode system matrix, and incorporates information about the radiation source energy prior and the ratio of Compton scattering event counts to photoelectric absorption event counts. Multimodal iterative reconstruction is then performed based on the weights, achieving stable multimodal imaging with a higher weighting of Compton imaging results for high-energy bands and a higher weighting of collimation-free mechanical collimation results for medium and low-energy bands. This method overcomes the problems of conventional iterative reconstruction algorithms, such as their inability to achieve targeted high-resolution imaging based on radiation source characteristics, low efficiency and sensitivity, and unstable imaging results, effectively improving the imaging energy range, field of view, and resolution of multimodal gamma cameras.

[0099] Figure 5 FIG. 1 is a structural diagram of a multi-mode iterative reconstruction device provided by an embodiment of the present invention. Figure 5 As shown, the multi-mode iterative reconstruction device may include the above Figure 4 Optionally, the multi-mode iterative reconstruction device 410 may include a first processor 2001 .

[0100] Optionally, the multi-mode iterative reconstruction device 410 may further include a memory 2002 and a transceiver 2003 .

[0101] The first processor 2001, the memory 2002 and the transceiver 2003 may be connected via a communication bus.

[0102] The following combination Figure 5 The components of the multi-mode iterative reconstruction device 410 are described in detail: The first processor 2001 is the control center of the multi-mode iterative reconstruction device 410 and can be a single processor or a collective term for multiple processing elements. For example, the first processor 2001 can be one or more central processing units (CPUs), an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement embodiments of the present invention, such as one or more digital signal processors (DSPs) or one or more field programmable gate arrays (FPGAs).

[0103] Optionally, the first processor 2001 may execute various functions of the multi-mode iterative reconstruction device 410 by running or executing a software program stored in the memory 2002 and calling data stored in the memory 2002 .

[0104] In a specific implementation, as an embodiment, the first processor 2001 may include one or more CPUs, such as Figure 5 CPU0 and CPU1 are shown in FIG.

[0105] In a specific implementation, as an embodiment, the multi-mode iterative reconstruction device 410 may also include multiple processors, such as Figure 5 1 and 2. The first processor 2001 and the second processor 2004 are shown in FIG. Each of these processors can be a single-core processor (single-CPU) or a multi-core processor (multi-CPU). A processor herein can refer to one or more devices, circuits, and / or processing cores for processing data (e.g., computer program instructions).

[0106] The memory 2002 is used to store the software program for executing the solution of the present invention, and is controlled by the first processor 2001 for execution. The specific implementation method can refer to the above method embodiment and will not be repeated here.

[0107] Alternatively, the memory 2002 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and instructions, a random access memory (RAM) or other type of dynamic storage device capable of storing information and instructions, an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, an optical disc storage (including a compact disc, laser disc, optical disc, digital versatile disc, Blu-ray disc, etc.), a magnetic disk storage medium or other magnetic storage device, or any other medium capable of carrying or storing desired program code in the form of instructions or data structures and capable of being accessed by a computer, but not limited thereto. The memory 2002 may be integrated with the first processor 2001 or exist independently and access the memory 2002 through the interface circuit ( Figure 5 (not shown) is coupled to the first processor 2001, which is not specifically limited in this embodiment of the present invention.

[0108] The transceiver 2003 is used to communicate with a network device or a terminal device.

[0109] Optionally, the transceiver 2003 may include a receiver and a transmitter ( Figure 5 The receiver is used to implement a receiving function, and the transmitter is used to implement a sending function.

[0110] Optionally, the transceiver 2003 may be integrated with the first processor 2001 or may exist independently and be reconstructed through the interface circuit ( Figure 5 (not shown) is coupled to the first processor 2001, which is not specifically limited in this embodiment of the present invention.

[0111] It should be noted that Figure 5 The structure of the multi-mode iterative reconstruction device 410 shown in the figure does not constitute a limitation on the router. The actual knowledge structure recognition device may include more or fewer components than shown in the figure, or combine certain components, or arrange the components differently.

[0112] In addition, the technical effects of the multi-mode iterative reconstruction device 410 can refer to the technical effects of the multi-mode iterative reconstruction method described in the above method embodiment, and will not be repeated here.

[0113] It should be understood that the first processor 2001 in the embodiment of the present invention may be a central processing unit (CPU), or may be other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components, etc. A general-purpose processor may be a microprocessor, or the processor may be any conventional processor, etc.

[0114] It should also be understood that the memory in the embodiments of the present invention may be volatile memory or non-volatile memory, or may include both volatile and non-volatile memory. The non-volatile memory may be read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or flash memory. The volatile memory may be random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of random access memory (RAM) are available, such as static RAM (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDR SDRAM), enhanced SDRAM (ESDRAM), synchronous link DRAM (SLDRAM), and direct rambus RAM (DR RAM).

[0115] The above embodiments can be implemented in whole or in part via software, hardware (e.g., circuits), firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions or computer programs. When loaded or executed on a computer, the processes or functions described in accordance with the embodiments of the present invention are fully or partially performed. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted from one computer-readable storage medium to another. For example, the computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired means (e.g., infrared, wireless, microwave, etc.). The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that contains a collection of one or more available media. The available medium can be magnetic media (e.g., floppy disks, hard disks, magnetic tapes), optical media (e.g., DVDs), or semiconductor media. The semiconductor media can be a solid-state drive.

[0116] It should be understood that the term "and / or" as used herein simply describes a relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A alone, A and B together, or B alone. A and B can be singular or plural. Furthermore, the character " / " as used herein generally indicates an "or" relationship between the associated objects, but it may also indicate an "and / or" relationship. For specific understanding, please refer to the context.

[0117] In this disclosure, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c" can mean: a, b, c, ab, ac, bc, or abc, where a, b, and c can be single or plural.

[0118] It should be understood that in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean 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.

[0119] Those skilled in the art will appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present invention.

[0120] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the above-described equipment, devices and units can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0121] In the several embodiments provided by the present invention, it should be understood that the disclosed devices, apparatuses and methods can be implemented in other ways. For example, the device embodiments described above are merely illustrative. For example, the division of the units is merely a logical function division. In actual implementation, there may be other division methods, such as multiple units or components can be combined or integrated into another device, or some features can be ignored or not executed. Another point is that the mutual coupling or direct coupling or communication connection shown or discussed can be through some interface, indirect coupling or communication connection of the device or unit, which can be electrical, mechanical or other forms.

[0122] The units described as separate components may or may not be physically separate, and 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 these units may be selected to achieve the purpose of this embodiment according to actual needs.

[0123] In addition, each functional unit in each embodiment of the present invention may be integrated into one processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit.

[0124] If the 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 the present invention, or the portion that contributes to the prior art, or the portion 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 for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in various embodiments of the present invention. The aforementioned storage media include various media that can store program code, such as USB flash drives, mobile hard drives, read-only memories (ROM), random access memories (RAM), magnetic disks, or optical disks.

[0125] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A multi-mode iterative reconstruction method, characterized in that: The method comprises: S1. Acquiring event information of gamma photons interacting with a three-dimensional position-sensitive semiconductor detection unit in a panoramic gamma camera system; S2. Acquire information based on the prior energy, the Compton scattering event count in the event information, and the photoelectric absorption event count in the event information, and calculate a weight based on the information; reconstruct a Compton sequence based on the prior energy, and construct a multimode system transmission matrix based on the reconstructed Compton sequence; S3. Perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix, output a stable high signal-to-noise ratio image, and determine the spatial distribution of the radiation source.

2. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The event information in S1 includes: timestamp, energy, three-dimensional position coordinates, action sequence and action type; The types of effects include: Compton scattering events and photoelectric absorption events; The timestamp is recorded by triggering the signal pulse captured by the data acquisition system in the panoramic gamma camera system; The energy is determined by the amplitude of the signal pulse; The three-dimensional position coordinates are determined by determining the two-dimensional transverse spatial coordinates of the photon action event through the anode response pixel position of the detector array, determining the action depth of the photon action event by analyzing the ratio of the cathode and anode signal amplitudes, and determining the three-dimensional position coordinates based on the two-dimensional transverse spatial coordinates and the action depth; The action sequence is determined by measuring the electron drift time and analyzing the timing information of the pulses corresponding to each interaction point; The interaction type is determined by the number of interaction points and the energy deposition pattern of each point in combination with the position information.

3. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The calculation weight in S2 is shown in the following formula (1): （1） Where, is the weight, is the optimization degree factor, is the prior energy of the radiation source, is the total number of Compton scattering events detected by the detector, It is the total number of photoelectric absorption events detected by the detector.

4. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The Compton sequence reconstruction in S2 includes: The interaction sequence in the full-energy double Compton coincidence event is determined by the magnitude of the deposited energy, and a Compton edge test is performed. The Compton edge test calculation formula is as shown in the following formula (2): （2） Where, For Compton Edge Energy, is the prior energy of the radiation source, is the electron rest mass, The speed of light.

5. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The multi-mode system transmission matrix in S2 includes: a non-collimation-mechanical collimation mode system transmission matrix and a Compton mode system transmission matrix; Among them, the transmission matrix of the non-collimation-mechanical collimation mode system is obtained by analytical calculation method, as shown in the following formula (3): （3） Where, is the transmission matrix of the non-collimation-mechanical collimation mode system, is the detector voxel, is the image plane pixel, is the attenuation coefficient of the high-density alloy, is the slave pixel intercepted by the mechanical collimator To detector voxel The radiation path, is the attenuation coefficient of the semiconductor detector, is the slave pixel intercepted by the detector To detector voxel The radiation path of the surface, is the number of slave pixels intercepted by the detector voxel To detector voxel Radiating paths from the center; The Compton mode system transfer matrix is ​​obtained by analytical calculation method, as shown in the following equation (4): （4） Where, is the transmission matrix of the Compton mode system, For Compton to meet the sequence of events, For the The number of pixels intercepted by the detector in the action sequence The radiation path to the Compton scattering site, for The Compton differential cross section, is the Compton scattering angle, For the The radiation path from the Compton scattering action position to the photoelectric absorption action position intercepted by the detector in each action sequence; The calculation formula of the Compton differential cross section is shown in the following formula (5): （5） Where, , is the prior energy of the radiation source, is the electron rest mass, The speed of light.

6. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The multi-mode iterative reconstruction in S3 is performed based on the weights and the multi-mode system transmission matrix, as shown in the following equation (6): （6） Where, for The new estimate after iterations, for The current estimate after iterations, is the image plane pixel, is the weight, For the total number of Compton-compliant events, For the The count of Compton measurements in the action sequence, is the transmission matrix of the Compton mode system, is the total number of pixels in the image space, for The normalized summation process of the first iteration The current estimated value of image pixels, is the image pixel index, is the total number of detector voxels, is the detector voxel The photon measurement count at is the transmission matrix of the non-collimation-mechanical collimation mode system, is the sensitivity matrix.

7. The multi-mode iterative reconstruction method according to claim 1, characterized in that: The panoramic gamma camera system includes: a three-dimensional position sensitive semiconductor detection unit and a coding plate module without a shielding layer; The three-dimensional position sensitive semiconductor detection unit includes: a three-dimensional position sensitive semiconductor, a dedicated integrated circuit chip, a field programmable logic gate array and a data acquisition system; The coding plate module without a shielding layer includes a coding plate and a side support layer.

8. A multi-mode iterative reconstruction device, wherein the multi-mode iterative reconstruction device is used to implement the multi-mode iterative reconstruction method according to any one of claims 1 to 7, characterized in that: The device comprises: an acquisition module, for acquiring event information of gamma photons interacting with a three-dimensional position-sensitive semiconductor detection unit in a panoramic gamma camera system; A construction module is configured to obtain information based on a priori energy, a count of Compton scattering events in the event information, and a count of photoelectric absorption events in the event information, and calculate a weight based on the information; reconstruct a Compton sequence based on the priori energy, and construct a multimode system transmission matrix based on the reconstructed Compton sequence; The output module is used to perform multi-mode iterative reconstruction based on the weights and the multi-mode system transmission matrix, output a stable high signal-to-noise ratio image, and determine the spatial distribution of the radiation source.

9. A multi-mode iterative reconstruction device, characterized in that: The multi-mode iterative reconstruction device includes: processor; A memory having computer-readable instructions stored thereon, wherein when the computer-readable instructions are executed by the processor, the method according to any one of claims 1 to 7 is implemented.

10. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores program code, which can be called by a processor to execute the method according to any one of claims 1 to 7.

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