Hyperhole collimator for gamma photon detection and design method thereof

Abstract

The invention provides a super-hole collimator for gamma photon detection, the super-hole collimator is provided with a collimator plate, a plurality of collimating holes which are irregularly distributed or randomly distributed are formed in the collimator plate, and when radioactive rays in an imaging view pass through the collimating holes, projection overlapping is formed on a gamma photon detector. And the superposition of the projection areas is at least two times of the detection area of the gamma photon detector. According to the multi-pinhole collimator, the limitation of a pinhole arrangement mode in a traditional multi-pinhole collimator on the number of pinholes is effectively overcome, a certain number of collimation holes are randomly arranged in the collimator, and the number of the collimation holes is far larger than that of the pinholes in the existing multi-pinhole collimator; according to the invention, the projection superposition area of radioactive rays in an imaging field of view on the detector through all the collimation holes meets the requirement, a super-hole collimator is formed, and the detection efficiency is obviously improved on the premise of ensuring the image resolution, so that the counting of gamma photons collected in unit time is improved, and the imaging collection time is effectively shortened.

Description

Technical Field

[0001] The present invention belongs to the field of nuclear medicine imaging technology, and particularly relates to a super-aperture collimator for gamma photon detection used to improve the sensitivity of nuclear medicine imaging systems, such as single photon emission computed tomography (SPECT), and a design method thereof. Background Art

[0002] Single Photon Emission Computed Tomography (SPECT) is an important nuclear medicine imaging method that has been widely used in pre-clinical drug research and clinical disease diagnosis. Spatial resolution and detection efficiency are two important technical indicators for measuring the performance of SPECT imaging. SPECT imaging requires a collimator to collimate the gamma rays to determine the incident direction of the gamma photons detected on the detector. Commonly used collimators include parallel hole collimators and multi-pinhole collimators. The radioactive source within the imaging field of view emits gamma photons uniformly in all directions. The collimator only allows gamma photons with a specific incident direction to pass through the collimator and be received by the detector. In this way, the incident direction of the detected gamma photons can be determined, which can be used for image reconstruction to obtain the three-dimensional distribution of the radioactive source within the imaging field of view. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art.

[0004] Although parallel-hole collimators are currently widely used in clinical practice, with the development of nuclear medicine, their spatial resolution and detection efficiency are unable to meet the higher clinical demands. Multi-pinhole collimators can improve detection efficiency and spatial resolution by narrowing the imaging field of view and designing appropriate pinhole magnification and pinhole arrangement. They are advantageous for imaging small organs such as the heart, thyroid gland, and brain. Therefore, multi-pinhole SPECT imaging systems are an important development direction in emission tomography technology. In traditional multi-pinhole collimator design, multiple pinholes need to be arranged on the collimator to improve detection efficiency. Currently, a regular arrangement is used. However, this arrangement limits the number of pinholes, resulting in a low overlap rate of projections of the imaging field of view through different holes / pinholes on the collimator onto the detector. As a result, the detection efficiency of existing multi-pinhole collimators is relatively low, with a typical value of around 0.05%. In clinical applications, a long data acquisition time is still required to obtain sufficient statistical counts for image reconstruction.

[0005] To this end, the present invention provides a super-aperture collimator for gamma photon detection, which greatly improves detection efficiency while ensuring image resolution.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A first aspect of the present invention provides a super-hole collimator for gamma photon detection, the super-hole collimator comprising a collimator plate on which a plurality of irregularly or randomly distributed collimating holes are formed. When radioactive rays within an imaging field of view pass through the collimating holes, overlapping projections are formed on a gamma photon detector. Moreover, the superposition of the projection areas formed on the gamma photon detector by the radioactive rays within the imaging field of view after passing through each collimating hole is at least twice the detection area of the gamma photon detector.

[0008] In some embodiments, the projection area of the radioactive rays within the imaging field of view through each collimating hole on the gamma photon detector is superimposed to 6 to 12 times the detection area of the gamma photon detector.

[0009] In some embodiments, the orientation of the collimating hole should satisfy that the normal vector of the center plane of the collimating hole passes through the center of the imaging field of view; the opening angle α of the collimating hole should satisfy the following formula:

[0010]

[0011] Where R is the radius of the imaging field of view; L is the distance from the center plane of the collimating hole to the center of the imaging field of view; and D is the aperture of the collimating hole.

[0012] In some embodiments, the collimator plate is divided into a plurality of sub-regions arranged in an array, and the collimation holes in at least two sub-regions are arranged in different ways. The arrangement of the collimation holes on the collimator plate further meets any one or a combination of the following requirements:

[0013] Requirement A: In each sub-region, the center points of any three or more collimating holes are not collinear;

[0014] Requirement B: Within each subregion, at least a portion of the coordinate increments of the collimating holes along the first direction are different, and the coordinate increments of three adjacent collimating holes along the first direction are different. At least a portion of the coordinate increments of the collimating holes along the second direction are different, and the coordinate increments of three adjacent collimating holes along the second direction are different. The first direction intersects the second direction.

[0015] Requirement C: Some sub-regions contain the same number of collimating holes, while the remaining sub-regions contain different numbers of collimating holes.

[0016] In some embodiments, the number of the collimating holes on the collimator plate is determined based on the requirement for the superposition of the projected areas of all the collimating holes on the gamma photon detector and the size of the collimator plate.

[0017] In some embodiments, the cross-sectional shapes of the collimating holes on the collimator plate are the same or different.

[0018] In some embodiments, the cross-sectional shape of the collimating hole is a circle or any regular polygon.

[0019] In some embodiments, the collimator plate is a flat plate or a curved plate.

[0020] A second aspect of the present invention provides a design method for a super-hole collimator according to any embodiment of the first aspect of the present invention, wherein the design method is used to determine the layout of each collimating hole in the super-hole collimator, comprising the following steps:

[0021] Step S1: constructing a relationship between target spatial resolution and collimating aperture according to a geometric optical model of gamma photons, and determining a range of collimating aperture according to the requirement of the target spatial resolution;

[0022] Step S2: Based on a real detection scenario, a simulation model with the superhole collimator and the gamma photon detector is constructed. Different numbers of collimating holes are irregularly or randomly distributed on the collimator plate of the simulation model, each serving as a corresponding superhole collimator design scheme. From all the design schemes, the design scheme that simultaneously meets the following three conditions is selected as a candidate design scheme:

[0023] Condition 1: The aperture of the collimating hole falls within the aperture range of the collimating hole determined in step S1;

[0024] Condition 2: The orientation of the collimator hole should make the normal vector of the center plane of the collimator hole pass through the center of the imaging field of view, and the opening angle α of the collimator hole satisfies the following formula:

[0025]

[0026] Where R is the radius of the imaging field of view; L is the distance from the center plane of the collimator hole to the center of the imaging field of view; D is the aperture of the collimator hole;

[0027] Condition 3: The projections of radioactive rays within the imaging field of view on the gamma photon detector after passing through different collimating holes overlap, and the superposition of the projection areas formed by the radioactive rays within the imaging field of view on the gamma photon detector after passing through each collimating hole should reach 6 to 12 times the detector area;

[0028] Step S3: Build a simulation environment for the nuclear medicine imaging system corresponding to each candidate design scheme, perform image reconstruction model simulation respectively, verify the reconstruction effect of the image reconstruction model based on Monte Carlo simulation experiments, and select the candidate design scheme that meets the set reconstruction effect index from all candidate design schemes as the optimal design scheme, thereby determining the layout of each collimating hole in the super-hole collimator.

[0029] In some embodiments, in step S1, for a pinhole collimator, the relationship between the target spatial resolution and the collimation hole diameter is as follows:

[0030]

[0031] Where SR is the target spatial resolution of the pinhole collimator, M is the magnification of the pinhole collimator, and SR is i is the intrinsic spatial resolution of the gamma photon detector, μ is the linear attenuation coefficient of the collimator plate for gamma photons; and / or

[0032] The image reconstruction model includes a thermal cylinder model; and / or

[0033] The reconstruction effect index is the degree of image artifacts.

[0034] The super-aperture collimator for gamma photon detection provided by the present invention has the following characteristics and beneficial effects:

[0035] The present invention effectively overcomes the limitations imposed by conventional multi-pinhole collimators on the number of pinholes. By irregularly or randomly arranging a certain number of collimating holes on the collimator, a number far greater than the number of pinholes in existing multi-pinhole collimators, the present invention ensures that the projected area of radioactive rays within the imaging field of view, passing through each collimating hole, on the detector meets the required projection area. This creates a super-hole collimator, thereby improving detection efficiency and thereby increasing the number of gamma photons collected per unit time, effectively shortening imaging acquisition time. The number of pinholes is determined by ensuring that the projected area of the imaging field of view, passing through all collimating holes, on the detector is at least twice, and preferably 6 to 12 times, the detector area. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 1 is a schematic structural diagram of an 80-pinhole super-aperture collimator provided by an embodiment of the first aspect of the present invention;

[0037] Figure 2 The radioactive rays passing through the imaging field of view Figure 1 The schematic diagram of the projection superposition of the 80-pinhole super-aperture collimator on the gamma photon detector is shown;

[0038] Figure 3 (a) and (b) are schematic diagrams of two other pinhole arrangements of the super-aperture collimator with 80 pinholes; Figure 3 (c) and (d) are respectively Figure 3 (a) and (b) are schematic diagrams of the corresponding projection superposition on the gamma photon detector;

[0039] Figure 4 Schematic diagram of the design requirements for a single collimating hole provided by an embodiment of the first aspect of the present invention;

[0040] Figure 5 is a flow chart of a method for designing a super-aperture collimator provided by an embodiment of the second aspect of the present invention;

[0041] Figure 6 Schematic diagram of the structure of applying the super-aperture collimator provided by an embodiment of the present invention to a dual-probe SPECT imaging system;

[0042] Figure 7 (a) is a schematic diagram of a thermal cylinder model established in an embodiment of the present invention. Figure 7 (b) to (h) are the reconstructed images corresponding to the case where the number of pinholes N is 40, 50, 60, 80, 100, 110, and 120, respectively. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical solutions and advantages of this application more clearly understood, this application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0044] On the contrary, this application covers any alternatives, modifications, equivalents, and solutions made within the spirit and scope of this application as defined by the claims. Furthermore, to facilitate a better understanding of this application, certain specific details are described in detail below in the detailed description of this application. Those skilled in the art will be able to fully understand this application without these details.

[0045] According to an embodiment of the first aspect of the present invention, a super-hole collimator for gamma photon detection is provided, in which N irregularly or randomly distributed collimating holes are formed on the collimator plate. When the radioactive rays in the imaging field of view pass through the collimating holes randomly distributed on the collimating plate, a projection overlap is formed on the gamma photon detector. The superposition of the projection areas of all the collimating holes should be much larger than the detection area of the gamma photon detector. The detection efficiency can be significantly improved while ensuring the image resolution. Combined with the existing maximum likelihood-expectation maximization (MLEM) iterative image reconstruction algorithm, the image reconstruction quality can be improved.

[0046] In order to understand the above-mentioned super-hole collimator more clearly, the following Figures 1 to 4 The super-aperture collimator of this embodiment is explained.

[0047] See also Figure 1 、 Figure 2This embodiment provides a super-hole collimator for gamma photon detection, which has a collimator plate 101, on which N=80 collimating holes 102 are formed in an irregular or randomly distributed manner. The imaging field of view and the gamma photon detector 201 are divided into two sides of the collimator plate 101. The imaging field of view should form an envelope of the detection object. When the radioactive rays in the imaging field of view pass through the collimating holes 102, they form a projection overlap on the gamma photon detector 201, and the superposition of the projection areas of the radioactive rays in the imaging field of view through all the collimating holes 102 should be at least twice the detection area of the gamma photon detector 201.

[0048] Preferably, the projection area of radioactive rays within the imaging field of view passing through all the collimating holes 102 on a single collimator plate 101 is superimposed to 6 to 12 times the detection area of the gamma photon detector 201 corresponding to the collimator plate 101, so as to greatly improve the detection efficiency in the center of the imaging field of view.

[0049] See also Figure 2 , represents the superposition of projections of the imaging field of view through all collimating holes 102 on the collimator plate 101 onto the gamma photon detector 201 in this implementation, and 202 represents the projection of the imaging field of view after passing through a single collimating hole 102. The sum of all projected areas is calculated to be 8.82 times the detection area of the gamma photon detector 201, which is within the design requirement of 6 to 12 times for this super-hole collimator. The detection efficiency at the center of the imaging field of view is 0.32%, significantly exceeding the 0.05% detection efficiency of conventional multi-pinhole collimators.

[0050] Furthermore, the number of collimating holes 102 included in the collimator plate 101 is determined according to the requirement for the superposition of the projected areas of all the collimating holes 102 on the gamma photon detector 201 and the size of the collimator plate 101 .

[0051] As a specific embodiment of the present invention, a device having an outer dimension of 345.6×256.6 mm is used. 2 When the collimator plate 101 is provided and the projection area of the imaging field passing through all the collimating holes 102 on the gamma photon detector 201 is required to be 6 to 12 times the detection area of the gamma photon detector 201, the number N of the collimating holes 102 arranged on the collimator plate 101 is 60 to 100.

[0052] Furthermore, the present invention overcomes the limitation on the number of collimating holes in conventional collimators by providing a plurality of irregularly or randomly distributed collimating holes on the collimator plate 101. The irregular or random distribution defined in the present invention is achieved by dividing the collimator plate 101 into a plurality of sub-regions arranged in an array, each sub-region containing at least three collimating holes 102, at least two sub-regions having different arrangements of the collimating holes 102, and the arrangement of the collimating holes 102 on the collimator plate 101 further meeting any one or a combination of the following requirements:

[0053] Requirement A: In each sub-region, the center points of any three or more collimating holes 102 are not collinear;

[0054] Requirement B: Within each sub-region, at least a portion of the coordinate increments of the collimating holes 102 along the first direction are different, and the coordinate increments of three adjacent collimating holes 102 along the first direction are different. At least a portion of the coordinate increments of the collimating holes 102 along the second direction are different, and the coordinate increments of three adjacent collimating holes 102 along the second direction are different, where the first direction intersects the second direction.

[0055] Requirement C: The number of collimating holes 102 contained in some sub-regions is the same, and the number of collimating holes 102 contained in the remaining sub-regions is different.

[0056] Optionally, the collimator plate 101 is evenly divided into several sub-regions, and the area of each sub-region is equal.

[0057] Preferably, at least 80% of the sub-regions in the collimator plate 10 have different collimation hole arrangements, and two adjacent sub-regions have different collimation hole arrangements.

[0058] Preferably, for requirement B, in a single sub-area, at least 80% of the collimating holes 102 have different coordinate increments along the first direction and the three adjacent collimating holes 102 have different coordinate increments along the first direction, and at least 80% of the collimating holes 102 have different coordinate increments along the second direction and the three adjacent collimating holes 102 have different coordinate increments along the second direction; optionally, two perpendicular directions on the collimating plate are respectively used as the first direction and the second direction.

[0059] Preferably, for requirement C, at least 50% of the sub-regions have different numbers of collimating holes 102 .

[0060] See also Figure 3Figures (a) to (d) are schematic diagrams of two other pinhole arrangements of the 80-pinhole super-aperture collimator provided in an embodiment of the present invention and their corresponding projection superposition diagrams formed on the gamma photon detector 201. The dotted lines in the figures are the boundaries of the sub-areas divided in this embodiment, which evenly divide the collimator plate 101 into sub-areas arranged in a 2×5 array, and the shape and area of each sub-area are relative.

[0061] Furthermore, the collimating holes on the collimator plate 101 should satisfy the requirement that the projection of the imaging field of view through the collimating holes at least partially covers the detection range of the detector.

[0062] Furthermore, the shapes of the collimating holes 102 on the collimator plate 101 can be the same or different, and the specific cross-sectional shape can be a circle or any regular polygon. The aperture of each collimating hole 102 is set according to the target spatial resolution requirement.

[0063] Further, see Figure 4 , is a schematic diagram of the design of a single collimating hole 102, where T is the thickness of the collimator plate 101, D is the diameter of the collimating hole (at the center plane), α is the opening angle of the collimating hole, R is the radius of the imaging field of view, and L is the distance from the center plane 103 of the collimating hole to the center 107 of the imaging field of view. The orientation of the collimating hole 102 should satisfy that the normal vector 104 of the center plane 103 of the collimating hole passes through the center 107 of the imaging field of view, and the two edge extension lines 105 and 106 of the collimating hole are tangent to the imaging field of view 108, so that the imaging field of view 108 can be imaged by the collimating hole 102. According to the above requirements, the opening angle α of the collimating hole 102 must satisfy:

[0064]

[0065] Furthermore, the collimator plate 101 is made of a heavy metal alloy with high atomic number and high density, such as tungsten and lead, so as to shield the rays emitted by the SPECT nuclide.

[0066] Furthermore, the collimator plate 101 may be a flat plate or a curved plate, and the corresponding plate type is selected according to the specific imaging application scenario.

[0067] See also Figure 5 According to the second aspect of the present invention, the design method of the super-hole collimator provided in the embodiment is used to determine the layout of each collimating hole in the super-hole collimator. The design scheme of this embodiment includes the following steps:

[0068] Step S1: Construct the relationship between the target spatial resolution and the collimator aperture based on the geometric optical model of gamma photons, and then determine the aperture range of the collimator aperture according to the target spatial resolution requirement. For a pinhole collimator, the relationship between the target spatial resolution and the collimator aperture is as follows:

[0069]

[0070] Where SR is the target spatial resolution of the pinhole collimator, M is the magnification of the pinhole collimator, and SR is i is the intrinsic spatial resolution of the gamma photon detector, D is the aperture (specifically, the diameter) of the collimating hole 102, α is the opening angle of the collimating hole 102, and μ is the linear attenuation coefficient of the collimator plate 101 for gamma photons;

[0071] Step S2: Based on a real detection scenario, a simulation model with the present super-hole collimator and gamma photon detector is constructed. Different numbers of collimating holes are arranged on the collimator plate of the simulation model in an irregular or random distribution, each serving as a corresponding super-hole collimator design scheme. From all the design schemes, the design scheme that simultaneously meets the following three conditions is selected as a candidate design scheme:

[0072] Condition 1: The aperture of the collimating hole 102 falls within the aperture range of the collimating hole determined in step S1;

[0073] Condition 2: The orientation of the collimating hole 102 should make the normal vector of the center plane of the collimating hole pass through the center of the imaging field of view, and the opening angle of the collimating hole 102 satisfies formula (1);

[0074] Condition 3: The projections of radioactive rays within the imaging field of view on the gamma photon detector after passing through different collimating holes 102 overlap, and the superposition of the projection areas formed by the radioactive rays within the imaging field of view on the gamma photon detector after passing through each collimating hole should reach 6 to 12 times the detector area;

[0075] Step S3: Build a simulation environment for a nuclear medicine imaging system (such as a SPECT system) corresponding to each candidate design scheme, perform image reconstruction model simulations including but not limited to a thermal cylinder model, and verify the reconstruction effect of the image reconstruction model based on a Monte Carlo simulation experiment; select a candidate design scheme that meets the reconstruction effect index requirements from all candidate design schemes as the optimal design scheme. Optionally, the reconstruction effect index is judged by the degree of image artifacts.

[0076] The effectiveness of the embodiments of the present invention will be verified below with reference to specific experimental data:

[0077] like Figure 6 The figure shows a commonly used dual-probe SPECT system in clinical practice. It has two gamma photon detectors 201 arranged at 90 degrees. Each gamma photon detector 201 is connected to a corresponding collimator plate 101 via a connector 203 on the side facing the imaging field of view 108. The detection object is located in the area of the imaging field of view 108. In this embodiment, the inherent spatial resolution of the gamma photon detector 201 is 3.4mm, and the effective detection area of the gamma photon detector 201 is 540×400mm.2 The outer dimensions of the collimator plate 101 are 345.6×256.6 mm. 2 The vertical distance between the gamma photon detector 201 and the collimator plate 101 is 148.1 mm, and the imaging field of view 108 is a sphere with a diameter of 19 cm.

[0078] First, based on the above data, the diameter of the collimating hole 102 is obtained as 4.5 mm according to step S1. Then, according to step S2, the number of collimating holes N = 40, 50, 60, 80, 100, 110, and 120 is randomly designed, and the diameter of the collimating hole is 4.5 mm. Seven super-hole collimators with different numbers of collimating holes are obtained. The accumulated projection area of the radioactive rays in the imaging field of view through all the collimating holes is approximately 457.8%, 566.6%, 674.0%, 882.4%, 1107.4%, 1212.2%, and 1317.7% of the detection area of the gamma photon detector. The detection efficiency at the center of the imaging field of view is calculated (the specific calculation method is a well-known calculation method in the art) as follows: 0.15%, 0.24%, 0.32%, 0.41%, 0.44%, and 0.48%, respectively. Finally, according to step S3, Monte Carlo simulation and image reconstruction based on the thermal cylinder model are performed on the dual-probe SPECT system, see Figure 7 In (a), the diameters of the thermal cylinders in the constructed thermal cylinder model are 6mm, 9mm, 12mm, 15mm, 18mm, and 21mm from small to large, and the acquisition time is set to be the same 30s. Figure 7 (b) to (h) are the reconstructed images corresponding to N = 40, 50, 60, 80, 100, 110, and 120, respectively. It can be seen that when N is between 60 and 100, the reconstructed image artifacts are relatively small, which is regarded as the optimal collimation hole layout scheme of this embodiment.

[0079] It should be noted that the projected area of radioactive rays within the imaging field of view defined in the embodiments of the present invention, as a function of the projection area of all collimating holes in the collimator plate onto the gamma photon detector, is 6 to 12 times the detection area of the gamma photon detector. This is applicable to all currently common clinical SPECT systems. Furthermore, experiments have shown that, while meeting the aforementioned projected overlap area requirement, the number of holes has a more significant impact on image reconstruction than their location.

[0080] In summary, the embodiments of the present invention increase the overlapping area of the projections by setting a large number of randomly or irregularly arranged pinholes, and at the same time set collimating holes that meet conditions one to three to avoid the generation of artifacts in the reconstructed image, thereby greatly improving the detection efficiency while ensuring image resolution.

[0081] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0082] Although the embodiments of the present disclosure have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and alterations may be made to the embodiments without departing from the principles and spirit of the present disclosure, the scope of which is defined by the claims and their equivalents.

Claims

1. A super-hole collimator for gamma photon detection, characterized in that: The super-hole collimator has a collimator plate, on which a plurality of irregularly or randomly distributed collimating holes are formed. When the radioactive rays in the imaging field of view pass through the collimating holes, overlapping projections are formed on the gamma photon detector, and the superposition of the projection areas formed by the radioactive rays in the imaging field of view passing through each collimating hole on the gamma photon detector is at least twice the detection area of the gamma photon detector.

2. The super-aperture collimator according to claim 1, characterized in that The projection area of the radioactive rays in the imaging field of view on the gamma photon detector through each collimating hole is superimposed to 6 to 12 times the detection area of the gamma photon detector.

3. The super-aperture collimator according to claim 1, characterized in that The orientation of the collimating hole should satisfy that the normal vector of the center plane of the collimating hole passes through the center of the imaging field of view; the opening angle α of the collimating hole should satisfy the following formula: Where R is the radius of the imaging field of view; L is the distance from the center plane of the collimating hole to the center of the imaging field of view; and D is the aperture of the collimating hole.

4. The super-aperture collimator according to claim 1, characterized in that The collimator plate is divided into a plurality of sub-regions arranged in an array, wherein the collimation holes in at least two sub-regions are arranged in different ways, and the arrangement of the collimation holes on the collimator plate further meets any one or a combination of the following requirements: Requirement A: In each sub-region, the center points of any three or more collimating holes are not collinear; Requirement B: Within each subregion, at least a portion of the coordinate increments of the collimating holes along the first direction are different, and the coordinate increments of three adjacent collimating holes along the first direction are different. At least a portion of the coordinate increments of the collimating holes along the second direction are different, and the coordinate increments of three adjacent collimating holes along the second direction are different. The first direction intersects the second direction. Requirement C: Some sub-regions contain the same number of collimating holes, while the remaining sub-regions contain different numbers of collimating holes.

5. The super-aperture collimator according to claim 1, characterized in that The number of the collimating holes on the collimator plate is determined according to the requirement for the superposition of the projected areas of all the collimating holes on the gamma photon detector and the size of the collimator plate.

6. The super-aperture collimator according to claim 1, characterized in that The cross-sectional shapes of the collimating holes on the collimator plate are the same or different.

7. The super-aperture collimator according to claim 1, characterized in that The cross-sectional shape of the collimating hole is a circle or any regular polygon.

8. The super-aperture collimator according to claim 1, characterized in that The collimator plate is a flat plate or a curved plate.

9. A method for designing a super-aperture collimator according to any one of claims 1 to 8, characterized in that: The design method is used to determine the layout of each collimating hole in the super-hole collimator, and includes the following steps: Step S1: constructing a relationship between target spatial resolution and collimating aperture according to a geometric optical model of gamma photons, and determining a range of collimating aperture according to the requirement of the target spatial resolution; Step S2: Based on a real detection scenario, a simulation model with the superhole collimator and the gamma photon detector is constructed. Different numbers of collimating holes are irregularly or randomly distributed on the collimator plate of the simulation model, each serving as a corresponding superhole collimator design scheme. From all the design schemes, the design scheme that simultaneously meets the following three conditions is selected as a candidate design scheme: Condition 1: The aperture of the collimating hole falls within the aperture range of the collimating hole determined in step S1; Condition 2: The orientation of the collimator hole should make the normal vector of the center plane of the collimator hole pass through the center of the imaging field of view, and the opening angle α of the collimator hole satisfies the following formula: Where R is the radius of the imaging field of view; L is the distance from the center plane of the collimator hole to the center of the imaging field of view; D is the aperture of the collimator hole; Condition 3: The projections of radioactive rays within the imaging field of view on the gamma photon detector after passing through different collimating holes overlap, and the superposition of the projection areas formed by the radioactive rays within the imaging field of view on the gamma photon detector after passing through each collimating hole should reach 6 to 12 times the detector area; Step S3: Build a simulation environment for the nuclear medicine imaging system corresponding to each candidate design scheme, perform image reconstruction model simulation respectively, verify the reconstruction effect of the image reconstruction model based on Monte Carlo simulation experiments, and select the candidate design scheme that meets the set reconstruction effect index from all candidate design schemes as the optimal design scheme, thereby determining the layout of each collimating hole in the super-hole collimator.

10. The design method according to claim 9, characterized in that: In step S1, for the pinhole collimator, the relationship between the target spatial resolution and the collimation hole diameter is as follows: Where SR is the target spatial resolution of the pinhole collimator, M is the magnification of the pinhole collimator, and SR is i is the intrinsic spatial resolution of the gamma photon detector, μ is the linear attenuation coefficient of the collimator plate for gamma photons; and / or The image reconstruction model includes a thermal cylinder model; and / or The reconstruction effect index is the degree of image artifacts.

Images