Weighted Back Projection for Asymmetric Cone Angle CT Artifacts
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Solution Overview
Problem
Existing 3D cone beam reconstruction algorithms face challenges with asymmetric cone angle artifacts due to the geometric structure of multi-source static CT, where the center of the ray source ring and detector ring are not in the same plane, leading to incorrect weight calculations and unresolved artifacts.
Innovation Solution
A weighted analytic filtered back projection reconstruction method that divides the reconstruction region into multiple weight regions based on the relative positions of the ray source and detector rings, assigns different initial weights, performs smooth transitions, and applies final weights for accurate reconstruction, compensating for asymmetric cone angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a symmetric weight calculation formula is used for cone beam reconstruction, then the reconstruction is simple and fast, but asymmetric cone angle artifacts occur when the ray source ring and detector ring centers are not in the same plane
Solution Approach 1:
The patent divides the reconstruction region into multiple weight regions based on the relative positions of the ray source ring and detector ring. Each region is assigned a different weight value to compensate for the asymmetric cone angle artifacts. This segmentation approach allows the system to handle the complexity of asymmetric geometry while maintaining computational efficiency.
Solution Approach 2:
The patent applies different weight values to different spatial regions of the reconstruction volume. Specifically, voxels are classified into near-end cone angle regions, far-end cone angle regions, and intermediate regions, each receiving tailored weight compensation. This local differentiation resolves the asymmetric artifacts without requiring a complete overhaul of the reconstruction algorithm.
2Manufacturing precision
If the ray source ring and detector ring are positioned in the same plane to maintain symmetry, then symmetric weight formulas work correctly, but the dose utilization rate of multi-row CT decreases
Solution Approach 1:
The patent explicitly embraces the asymmetric geometric configuration of multi-source static CT by developing weight calculation methods that account for the staggered positions of the ray source ring and detector ring. Instead of forcing symmetry, the algorithm calculates separate weights for near-end and far-end cone angles, enabling the system to utilize the asymmetric geometry for improved dose efficiency while maintaining reconstruction accuracy.
3Device complexity
If a single weight value is assigned to all regions, then the calculation is simple, but asymmetric cone angle artifacts cannot be removed
Solution Approach 1:
The patent implements a dynamic weighting scheme where weight values are adjusted based on the specific geometric configuration and position of each voxel in the reconstruction volume. The weight for each voxel is determined by its location relative to the ray source and detector rings, allowing the algorithm to adapt to the asymmetric geometry and eliminate artifacts while maintaining computational feasibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method effectively reduces artifacts, improves the reconstructable range and accuracy of CT scans, reduces the required radiation dose, and extends the applicability of symmetric weight formulas to asymmetric cone angle configurations.
Implementation Method 1
acquiring the projection data volume of voxel points in each weight region irradiated by X-rays
Data Source
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AI summary
Disclosed in the present invention are a weighted analytic filtered back projection reconstruction method and system for asymmetric cone angle artifacts. The method comprises the following steps: dividing a reconstruction area into a plurality of weight regions on the basis of relative positions of a ray source ring and a detector ring, wherein the ray source ring and the detector ring are mutually staggered to form asymmetric cone angle artifacts; acquiring the projection data volume of voxel points in each weight area irradiated by X-rays; according to the projection data volume of the voxel points in each weight area irradiated by the X-rays, assigning a different initial weight to each weight area; performing smooth transition on the initial weight of each weight area by means of a transition weight to form a final weight assigned to each weight area; and according to different final weights of the weight regions, performing final weighted analytic reconstruction on projection data p (α, β, γ) collected under large cone beam opening angle geometry, to acquire a back projection image. The method can effectively estimate and compensate for asymmetric cone angle artifacts caused by staggering of a ray source and a detector.