Method and system for weighted analysis, filtering and backprojection reconstruction for asymmetric cone angle artifacts

Abstract

The present invention discloses a method and system for weighted analysis, filtering, and backprojection reconstruction for asymmetric cone-angle artifacts. The method includes the steps of: dividing a reconstruction region into multiple weighted zones based on the relative positions of a radiation source ring and a detector ring, where the radiation source ring and the detector ring are offset from each other to form asymmetric cone-angle artifacts; acquiring the amount of projection data of voxel points in each weighted zone irradiated with X-rays; assigning different initial weights to each weighted zone based on the amount of projection data of voxel points in each weighted zone irradiated with X-rays; smoothly transitioning the initial weights of each weighted zone using transfer weighting to form final weights assigned to each weighted zone; and performing a final weighted analysis and reconstruction on projection data p(α,β,γ) acquired at a large geometric cone-beam flare angle based on the different final weights of each weighted zone to obtain a backprojection image. This method can effectively estimate and correct asymmetric cone-angle artifacts caused by the misalignment of the radiation source and the detector.

Description

[Technical Field]

[0001] The present invention relates to a method for weighting analysis and filtering and reconstructing backprojection for asymmetric cone angle artifacts, and a system for reconstructing the corresponding backprojection, which belongs to the technical field of medical imaging. [Background technology]

[0002] As the number of detector rows in CT systems continues to increase, the problem of cone angle artifacts faced by 3D cone-beam reconstruction algorithms becomes more pronounced. Therefore, multi-source static CT has emerged, but its unique geometric structure (the centers of the radiation source ring and the detector ring are not coplanar) makes the originally symmetric cone angle artifacts non-symmetric, creating new challenges for reconstruction algorithms.

[0003] To improve the dose utilization of multi-row CT, Grimmer et al. proposed a method to extend FDK (xFDK). This method involves correcting the weighting of the cone angle zones by analyzing and calculating it, as shown in Figure 1. However, this method only applies to the symmetric cone angle of conventional multi-row spiral CT, and the weighting calculation formula only applies to the far-end cone angle of asymmetric cone angles. However, calculating the weighting of the near-end cone angle can produce incorrect results and make it impossible to remove artifacts. Summary of the Invention [Problem to be solved by the invention]

[0004] The main technical problem to be solved by the present invention is to provide a method for weighting analysis and filtering and reconstructing backprojection for asymmetric cone angle artifacts.

[0005] Another technical problem that the present invention seeks to solve is to provide a system for reconstructing the backprojection of asymmetric cone angle artifacts.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solutions.

[0007] According to a first aspect of an embodiment of the present invention, there is provided a method for weighted analysis and filtering and reconstruction backprojection for asymmetric cone angle artifacts, the method comprising the following steps: Dividing the reconstructed region into a plurality of weighted zones based on the relative positions of a radiation source ring and a detector ring, the radiation source ring and the detector ring being offset from one another to produce asymmetric cone angle artifacts; obtaining a quantity of projection data for voxel points in each of the weighted zones irradiated with X-rays; assigning different initial weights to each of the weighting zones based on the amount of projection data of voxel points in each of the weighting zones irradiated with X-rays; using transfer weights to smoothly transition the initial weights of each of the weighting zones to form the final weights assigned to each of the weighting zones; and performing a final weighted analytical reconstruction on the projection data p(α, β, γ) collected at a large geometric cone-beam flare angle based on different final weights for each of the weighting zones, thereby obtaining a back-projected image.

[0008] Preferably, the step of dividing the reconstructed region into a plurality of weighted zones based on the relative positions of the radiation source ring and the detector ring specifically includes: A step of constructing a spatial coordinate system by defining the center of the detector ring as a circle center O, the axis of the detector ring as a Z axis, the horizontal radial direction of the detector ring as an X axis, and the vertical radial direction of the detector ring as a Y axis, JPEG2025542512000002.jpg23163The process includes a step of dividing the reconstructed region into a total of eight weighted zones, A to H, using the X-ray cone beam flare angles on both sides of the Z axis.

[0009] Here, the angular range ω(v,θ) of the eight weighted zones irradiated with X-rays is: JPEG2025542512000003.jpg75164

[0010] Here, c1=cot γ1, c2=cot γ2, and θ1 and θ2 are defined as follows: JPEG2025542512000004.jpg62138

[0011] where R S represents the vertical distance from the radiation source to the center of the FOV, z represents the Z-axis coordinate of the voxel point v, r represents the length of the vector (x, y) on the XY plane, and φ represents the included angle between the vector (x, y) and the Y-axis on the XY plane.

[0012] Preferably, the quantity φ(v,θ) of projection data of a voxel point in each of said weighted zones irradiated with X-rays is calculated using the following formula: JPEG2025542512000005.jpg68130

[0013] Preferably, the step of assigning a different initial weight to each of said weighting zones specifically comprises: Dividing the eight weighted zones A to H into an unexposed region, a partially irradiated region, a fully irradiated region, and a non-fixed irradiated region based on the amount of projection data φ(v, θ) of the voxel points in each of the weighted zones irradiated with X-rays; assigning an initial weight of 0 to the unexposed regions; JPEG2025542512000006.jpg31165

[0014] Preferably, weighted zones A and H are divided into unexposed areas, weighted zones B and G are divided into areas with an exposure of less than 180 degrees, weighted zones C and F are divided into areas with an exposure of 180 degrees or more but less than 360 degrees, weighted zone D is divided into areas that are fully exposed at 360 degrees, and weighted zone E is divided into areas with non-fixed exposure.

[0015] For the area where the irradiance is greater than or equal to 180 degrees but less than 360 degrees, it belongs to weighting zone C, i.e., c2z-R S >R S If -c1z is satisfied, JPEG2025542512000007.jpg60135

[0016] For the area where the irradiance is greater than or equal to 180 degrees but less than 360 degrees, it belongs to the weighting zone F, i.e., R S -c1z≧c2z-R S If JPEG2025542512000008.jpg77167, Here, the function s(t) = sin(πt / 2).

[0017] For areas with less than 180 degrees of illumination and / or non-fixed illumination areas, JPEG2025542512000009.jpg43165

[0018] Preferably, the step of smoothly transitioning the initial weightings of each of said weighting zones using transfer weights to form the final weightings assigned to each of said weighting zones comprises specifically: To smoothly transition the initial weighting of each of the weighting zones, the transfer weighting W T By introducing (ν,θ), the final weighting JPEG2025542512000010.jpg13134 is included.

[0019] Here, for an area that is not fully illuminated in 360 degrees, WT (ν,θ)=1, For a fully illuminated area in 360 degrees, JPEG2025542512000011.jpg51164

[0020] Preferably, the final weighted analytical reconstruction is performed according to the following formula: JPEG2025542512000012.jpg16127 where p(θ,ξ,γ) is the geometric parallel beam projection data obtained after permuting the weights of p(α,β,γ), ξ is the lateral index variable of the permuted projection, and h(ξ) is the filtering kernel.

[0021] According to a second aspect of an embodiment of the present invention, there is provided a system for reconstructing a backprojection of an asymmetric cone angle artifact, comprising a processor and a memory, the processor reading a computer program stored in the memory, the system for reconstructing a backprojection performing the following operations: dividing the reconstructed region into a plurality of weighted zones based on the relative positions of a radiation source ring and a detector ring, the radiation source ring and the detector ring being offset from one another to produce asymmetric cone angle artifacts; assigning different initial weights to each of the weighting zones based on the amount of projection data of voxel points in each of the weighting zones irradiated with X-rays; smoothly transitioning the initial weightings of each of the weighting zones using transfer weightings to form the final weightings assigned to each of the weighting zones; The final weighting is used to perform analytical reconstruction and backprojection on the projection data p(α,β,γ) collected at a large cone-beam flare angle to obtain a backprojection image based on the different final weightings for each weighting zone.

[0022] Preferably, the radiation source ring is composed of a plurality of X-ray sources arranged in a circular pattern, the detector ring is composed of a plurality of X-ray detectors arranged in a circular pattern, and the detector ring is located inside the radiation source ring.

[0023] According to a third aspect of an embodiment of the present invention, there is provided a computer-readable storage medium containing program instructions which, when executed by a processor, implement the above-mentioned method for weighted analysis, filtering and reconstruction of backprojection. [Effects of the Invention]

[0024] Compared with conventional techniques, the weighting analysis, filtering, and backprojection reconstruction method provided by the present invention can effectively estimate and correct asymmetric cone angle artifacts caused by misalignment between the radiation source and the detector. Performing weighting on the reconstructed region based on this method significantly improves the reconstructable range of a single axial scan of static CT, significantly improving the uniformity and accuracy of CT values ​​in the edge layer of FBP reconstruction analyzed in axial scans. Expanding the reconstructable range indirectly improves the radiation dose utilization rate of static CT and effectively reduces the radiation dose required for static CT imaging. Furthermore, by extending the weighting formula, which was previously only applicable to symmetric cone angle configuration systems, to also apply to asymmetric cone angles, this method can now be applied to static CT geometric configurations. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a schematic diagram illustrating a geometric configuration applicable to the xFDK weighting method in the prior art. [Figure 2] FIG. 1 is a schematic diagram illustrating a geometric configuration applicable to the bixFDK weighting method in an embodiment of the present invention. [Figure 3]FIG. 1 is a flowchart diagram of a method for weighting analysis and filtering and reconstruction backprojection for asymmetric cone angle artifacts provided by an embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a radiation source ring and a detector ring in a spatial coordinate system in an embodiment of the present invention. [Figure 5] FIG. 10 is a diagram illustrating losses of a radiation source ring and a detector ring in a spatial coordinate system in an embodiment of the present invention. [Figure 6] FIG. 10 is a schematic diagram showing regions into which a reconstructed region is divided in an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic diagram showing a projection image reconstructed using a general FDK algorithm. [Figure 8] FIG. 1 is a schematic diagram illustrating a projection image reconstructed using the general xFDK weighting algorithm. [Figure 9] FIG. 1 is a schematic diagram illustrating a projection image reconstructed using the bixFDK weighting algorithm in an embodiment of the present invention. [Figure 10] FIG. 1 is a schematic diagram illustrating a system structure for reconstructing the backprojection of asymmetric cone angle artifacts provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0026] The technical contents of the present invention will be described in detail and specifically below in combination with the accompanying drawings and specific embodiments.

[0027] As shown in Figure 2, an embodiment of the present invention first provides a method for weighting analysis, filtering, and backprojection reconstruction for asymmetric cone angle artifacts. The method for calculating backprojection weighting coefficients derived based on the analysis corrects the cone angle shadow caused by incomplete data, and processes the near-end and far-end cone angles of the asymmetric cone angle artifact separately to obtain correct weighting at both ends, thereby correctly correcting the cone angle. Compared with existing cone angle weighting reconstruction algorithms, this method has the advantages of accurate correction, fast calculation speed, and no introduction of other artifacts.

[0028] As shown in FIG. 3, the method for weighting analysis and filtering and reconstruction back projection for asymmetric cone angle artifacts provided by the embodiment of the present invention specifically includes steps S1 to S4.

[0029] S1: Divide the reconstructed region into multiple weighted zones based on the relative positions of the source ring and the detector ring.

[0030] Specifically, in this embodiment, the radiation source ring and the detector ring are offset from each other to form an asymmetric cone angle artifact. Referring to Figures 4 and 5, a spatial coordinate system is constructed with the center of the detector ring as the circle center O, the axis of the detector ring as the Z axis, the horizontal radial direction of the detector ring as the X axis, and the vertical radial direction of the detector ring as the Y axis. In the spatial coordinate system, the cone beam flare angle of the X-rays received by the detector ring is in the range [γ2, γ1], and the rotation angle φ corresponding to the coordinates v = (x, y, z) of the voxel point satisfies x = -rsinφ and y = rcosφ.

[0031] Referring to FIG. 6, in this embodiment, the reconstructed region is divided into a total of eight weighted zones, A to H, using the X-ray cone beam flare angles on both sides of the Z axis.

[0032] Here, the angular range ω(v,θ) of the eight weighted zones irradiated with X-rays is: JPEG2025542512000013.jpg76166

[0033] Here, c1=cot γ1, c2=cot γ2, and θ1 and θ2 are defined as follows: JPEG2025542512000014.jpg61146

[0034] where R S represents the vertical distance from the radiation source to the center of the FOV, z represents the Z-axis coordinate of the voxel point v, r represents the length of the vector (x, y) on the XY plane, and ψ represents the included angle between the vector (x, y) and the Y-axis on the XY plane.

[0035] S2: Obtain the amount of projection data of the voxel points in each of the weighted zones irradiated with X-rays.

[0036] Specifically, in this embodiment, the amount of projection data φ(v, θ) of a voxel point in each weighted zone irradiated with X-rays is calculated using the following formula: JPEG2025542512000015.jpg67140

[0037] S3: Assign a different initial weight to each weighting zone based on the amount of projection data of the voxel points in each weighting zone that are irradiated with X-rays.

[0038] In this embodiment, based on the amount of projection data of the voxel points in each weighting zone irradiated with X-rays, a total of eight weighting zones A to H are divided into four categories: an unirradiated area, a partially irradiated area, a fully irradiated area, and a non-fixed irradiated area; Unirradiated areas are assigned an initial weight of 0, The partial illumination area and non-fixed illumination area are initially weighted 0. <W PS Assign (v,θ)<1, The fully illuminated area has an initial weighting W FS Assign (v,θ)=1.

[0039] Specifically, weighted zone A and weighted zone H are divided into non-illuminated areas, weighted zone B and weighted zone G are divided into areas with an illumination intensity of less than 180 degrees, weighted zone C and weighted zone F are divided into areas with an illumination intensity of 180 degrees or more but less than 360 degrees, weighted zone D is divided into an area that is fully illuminated at 360 degrees, and weighted zone E is divided into a non-fixed illumination area. Here, the area with an illumination intensity of less than 180 degrees and the area with an illumination intensity of 180 degrees or more but less than 360 degrees both belong to the partial illumination area, but the specific initial weights assigned are 0. <W PS (ν,θ)<1 has a specific difference, specifically as follows:

[0040] For the area where the irradiance is greater than or equal to 180 degrees but less than 360 degrees, it belongs to weighting zone C, i.e., c2z-R S >R S If -c1z is satisfied, JPEG2025542512000016.jpg82167

[0041] For the area where the irradiance is greater than or equal to 180 degrees but less than 360 degrees, it belongs to the weighting zone F, i.e., R S -c1z≧c2z-R S If JPEG2025542512000017.jpg61130Here, the function s(t) = sin(πt / 2).

[0042] For areas with an illumination intensity of less than 180 degrees and / or non-fixed illumination areas, i.e., if they belong to weighting zone B, weighting zone G and / or weighting zone E, For the area that is fully illuminated at 34150360 degrees, i.e., belongs to weighting zone D, all data are assigned the same weight W FS (v,θ)=1 is assigned.

[0043] S4: The transfer weights are used to smoothly transition the initial weights of each weighting zone to form the final weights assigned to each of said weighting zones.

[0044] Specifically, in this embodiment, in order to smoothly transition the initial weighting of each weighting zone, the transfer weighting W T By introducing (ν,θ), the final weight assigned to each weighting zone is Form JPEG2025542512000019.jpg15145.

[0045] Here, for the area that is not completely illuminated in 360 degrees (i.e., the remaining seven weighted zones other than weighted zone D), W T (ν,θ)=1, For a fully illuminated area at 360 degrees (i.e.: weighted zone D), JPEG2025542512000020.jpg47133, Δr=R M 2 / 2R S , r0=min(R S -c1z,c2z-R S )-Δr, and R M is the radius of the FOV (as shown in Figure 4).

[0046] S5: Based on the different final weightings of each weighting zone, a backprojection image is obtained by performing a final weighted analytical reconstruction on the projection data p(α,β,γ) collected at a large geometric cone-beam flare angle.

[0047] Specifically, in this embodiment, the final weighted analytical reconstruction is performed by the following equation: JPEG2025542512000021.jpg16127 where p(θ,ξ,γ) is the geometric parallel beam projection data obtained after permuting the weights of p(α,β,γ), ξ is the lateral index variable of the permuted projection, and h(ξ) is the filtering kernel.

[0048] Referring to Figures 7 to 9, Figure 7 is a schematic diagram showing a projection image reconstructed using a general FDK algorithm, Figure 8 is a schematic diagram showing a projection image reconstructed using a general xFDK weighting algorithm, and Figure 9 is a schematic diagram showing a projection image reconstructed using the bixFDK weighting algorithm in an embodiment of the present invention. As can be seen from the figures, the results of reconstruction using the general FDK algorithm show obvious cone angle shadows on the upper and lower edges. The xFDK algorithm can only reduce the shadows on the upper edge, but shadows still exist in the area below the dotted line on the lower edge. However, the bixFDK algorithm in this embodiment significantly reduces all of the shadows on the upper and lower edges.

[0049] Thus, through steps S1 to S5, we have designed and implemented a method for removing asymmetric cone angle artifacts in static CT analysis and reconstruction. Using this method, asymmetric cone angle artifacts caused by misalignment between the radiation source and the detector can be effectively estimated and corrected. Performing weighting on analytical reconstruction based on this method significantly improves the reconstructible range of a single axial scan of static CT, significantly improving the uniformity and accuracy of CT values ​​in the edge layer of FBP reconstruction analyzed in axial scans. Expanding the reconstructible range indirectly improves the radiation dose utilization rate of static CT and effectively reduces the radiation dose required for static CT imaging. Furthermore, in this embodiment, the weighting formula, which was previously only applicable to symmetric cone angle configuration systems, is extended to be applicable to asymmetric cone angles, making it possible to understand that this method can also be applied to static CT geometric configurations.

[0050] The present invention further provides a system for reconstructing backprojection based on the above-mentioned method for reconstructing weighted analysis, filtering, and backprojection. As shown in Fig. 10, the system for reconstructing backprojection includes one or more processors 21 and a memory 22. Here, the memory 22 is connected to the processor 21 and is used to store one or more programs. When the one or more programs are executed by the one or more processors 21, the one or more processors 21 realize the method for reconstructing weighted analysis, filtering, and backprojection in the above-mentioned embodiment.

[0051] The processor 21 is used to control the overall operation of the backprojection reconstruction system, completing all or part of the steps of the weighting analysis, filtering, and backprojection reconstruction method. The processor 21 may be a central processing unit (CPU), a graphics processor (GPU), a field programmable logic gate array (FPGA), an application-specific integrated circuit (ASIC), a digital signal processing (DSP) chip, etc. The memory 22 is used to store various types of data to support the operation of the backprojection reconstruction system. These data include, for example, instructions used in any application or method operating in the backprojection reconstruction system, and data related to the application. The memory 22 can be implemented by any type of volatile or non-volatile storage device, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic memory, flash memory, etc., or a combination thereof.

[0052] In an exemplary embodiment, the backprojection reconstruction system may be specifically implemented by a computer chip or entity, or by a product having certain functionality for performing the above-described weighting analysis, filtering, and backprojection reconstruction method and achieving technical results consistent with the above-described method. A typical embodiment is a computer. Specifically, the computer may be, for example, a personal computer, a laptop computer, an in-vehicle human-computer interaction device, a mobile phone, a camera phone, a smartphone, a personal digital assistant, a media player, a navigation device, an email device, a game console, a tablet computer, a wearable device, or any combination of these devices.

[0053] In another exemplary embodiment, the present invention further provides a computer-readable storage medium including program instructions, which, when executed by a processor, perform the steps of the method for reconstructing weighted analysis, filtering, and backprojection in any one of the above-described embodiments. For example, the computer-readable storage medium may be the above-described memory including program instructions, and the above-described program instructions, when executed by a processor of a system for reconstructing backprojection, can complete the above-described method for reconstructing weighted analysis, filtering, and backprojection, and achieve technical effects consistent with the above-described method.

[0054] To summarize the above, the method and system for weighting analysis and filtering and backprojection reconstruction for asymmetric cone angle artifacts provided by the embodiments of the present invention has the following beneficial effects: 1. Asymmetric cone angle artifacts caused by misalignment between the radiation source and detector can be effectively estimated and corrected. By performing weighting on the reconstructed region based on this method, the reconstructable range of a single axial scan in static CT can be significantly improved, effectively reducing the radiation dose required for static CT imaging. 2. By extending the weighting formula, which was previously only applicable to configuration systems with symmetric cone angles, to also apply to systems with asymmetric cone angles, this method can now be applied to geometric configurations of static CT.

[0055] The above is a detailed description of the method and system for weighting analysis, filtering and backprojection reconstruction for asymmetric cone angle artifacts provided by the present invention. For those skilled in the art, any obvious modifications made to the present invention without departing from the essential content of the present invention will constitute infringement of the patent right of the present invention, and will incur corresponding legal liability.

Claims

1. A method for weighting analysis and filtering and reconstruction backprojection for asymmetric cone angle artifacts, comprising: The method comprises the following steps: Dividing the reconstructed region into a plurality of weighted zones based on the relative positions of a radiation source ring and a detector ring, the radiation source ring and the detector ring being offset from one another to produce asymmetric cone angle artifacts; obtaining a quantity of projection data for voxel points in each of the weighted zones irradiated with X-rays; assigning a different initial weight to each of the weighting zones based on the amount of projection data of voxel points in each of the weighting zones irradiated with X-rays; using transfer weights to smoothly transition the initial weights of each of the weighting zones to form the final weights assigned to each of the weighting zones; and performing a final weighted analysis reconstruction on the projection data p(α, β, γ) collected at a large geometric cone beam flare angle based on different final weights of each of the weighting zones to obtain a back projection image.

2. The step of dividing the reconstructed region into a plurality of weighted zones based on the relative positions of the radiation source ring and the detector ring specifically includes: A step of constructing a spatial coordinate system by defining the center of the detector ring as a circle center O, the axis of the detector ring as a Z axis, the horizontal radial direction of the detector ring as an X axis, and the vertical radial direction of the detector ring as a Y axis, In the spatial coordinate system, the cone beam flare angle of the X-rays received by the detector ring is [γ ２ , γ １ ] range, and dividing the reconstructed region into a total of eight weighted zones A to H using X-ray cone beam flare angles on both sides of the Z axis; where the angular range ω(v, θ) of the eight weighted zones irradiated with X-rays is: Here, c １ =cot γ １ , c ２ =cot γ ２ and θ 1 and θ 2 is defined as follows: Here, R Ｓ 2. The method for weighted analysis and filtering and backprojection reconstruction according to claim 1, wherein: represents the vertical distance from the radiation source to the center of the FOV; z represents the Z-axis coordinate of the voxel point v; r represents the length of the vector (x, y) in the XY plane; and φ represents the angle formed by the vector (x, y) and the Y-axis in the XY plane.

3. The method for weighted analysis and filtering and backprojection reconstruction according to claim 2, characterized in that the quantity φ(v, θ) of projection data of voxel points in each weighted zone irradiated with X-rays is calculated using the following formula:

4. The step of assigning a different initial weight to each of the weighting zones specifically includes: Dividing a total of eight weighting zones A to H into an unexposed region, a partially exposed region, a fully exposed region, and a non-fixed exposed region based on the amount of projection data φ(v, θ) of the voxel points in each of the weighting zones irradiated with X-rays; assigning an initial weight of 0 to the unexposed regions; 4. The method of claim 3, further comprising:

5. Weighted zone A and weighted zone H are divided into unexposed areas, weighted zone B and weighted zone G are divided into areas with an exposure of less than 180 degrees, weighted zone C and weighted zone F are divided into areas with an exposure of 180 degrees or more but less than 360 degrees, weighted zone D is divided into an area that is fully exposed at 360 degrees, and weighted zone E is divided into an unfixed exposed area; For the area where the irradiance is 180 degrees or more but less than 360 degrees, it belongs to the weighting zone C, i.e., c ２ z-R Ｓ >R Ｓ -c １ If z is satisfied, The area where the irradiance is greater than or equal to 180 degrees and less than 360 degrees belongs to the weighting zone F, i.e., R Ｓ -c １ z ≧ c ２ z-R Ｓ If where the function s(t) = sin(πt / 2) For areas with illumination less than 180 degrees and / or non-fixed illumination areas: For a fully illuminated area in 360 degrees, all data are weighted equally. FS The method for weighted analysis and filtering and reconstruction of backprojection according to claim 4, characterized in that (ν, θ) is assigned.

6. The step of smoothly transitioning the initial weightings of each of the weighting zones using transfer weights to form the final weightings assigned to each of the weighting zones specifically includes: To smoothly transition the initial weighting of each of the weighting zones, the transfer weighting W Ｔ By introducing (ν, θ), the final weighting forming a Here, in the case of an area that is not completely illuminated in 360 degrees, W Ｔ (ν, θ)=1, For a fully illuminated area in 360 degrees, Δr=R Ｍ ２ / 2R Ｓ , r ０ = min(R Ｓ -c １ z, c ２ z-R Ｓ ) -Δr, and R Ｍ The method for weighted analysis and filtering and backprojection reconstruction according to claim 5, characterized in that: is the radius of the FOV.

7. The final weighted analytical reconstruction is performed by the following equation: The method for weight analysis and filtering and backprojection reconstruction according to claim 6, characterized in that p(θ,ξ,γ) is the geometric parallel beam projection data obtained after rearranging the weight of p(α,β,γ), ξ is the horizontal index variable of the rearranged projection, and h(ξ) is the filtering kernel.

8. 1. A system for reconstructing a backprojection, comprising: a processor and a memory, the processor reading a computer program in the memory and performing the following operations: dividing the reconstructed region into a plurality of weighted zones based on the relative positions of a radiation source ring and a detector ring, the radiation source ring and the detector ring being offset from one another to produce asymmetric cone angle artifacts; assigning different initial weights to each of the weighting zones based on the amount of projection data of voxel points in each of the weighting zones irradiated with X-rays; smoothly transitioning the initial weightings of each of the weighting zones using transfer weightings to form the final weightings assigned to each of the weighting zones; A backprojection reconstruction system, characterized in that it is used to perform an operation of performing a final weighted analytical reconstruction on projection data p(α, β, γ) collected at a large geometric cone beam flare angle so as to obtain a backprojection image based on different final weights of each of the weighting zones.

9. 9. The backprojection reconstruction system of claim 8, wherein the radiation source ring is composed of a plurality of X-ray sources arranged in a circular pattern, the detector ring is composed of a plurality of X-ray detectors arranged in a circular pattern, and the detector ring is located inside the radiation source ring.

10. A computer-readable storage medium containing program instructions, A computer-readable storage medium, characterized in that, when the program instructions are executed by a processor, the method for weighted analysis and filtering and backprojection reconstruction according to any one of claims 1 to 7 is realized.

Images