Fan-to-Parallel Data Rebinning for Unequal Gamma Angle CT Systems
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Solution Overview
Problem
Third-generation CT systems with flat module detector arrays face issues with ring artifacts due to unequal gamma angle geometry, making traditional fan-to-parallel data rebinning algorithms ineffective, which leads to inaccurate reconstruction and artifacts in CT imaging.
Innovation Solution
A method and apparatus for CT systems that involve obtaining fan beam projection data, acquiring geometric structure parameters of the flat module detector array, and rebinning data from fan beam to parallel beam using these parameters, incorporating re-sampling and interpolation techniques to establish a corresponding relation between the data sets, and generating CT images using filtered back projection algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional fan-to-parallel data rebinning algorithms are used, then data conversion can be performed, but ring artifacts appear and reconstruction accuracy deteriorates due to unequal gamma angle geometry
Solution Approach 1:
The patent changes the rebinning parameters and geometric model to account for unequal gamma angles in flat module detector arrays. By modifying the rebinning equations to incorporate the actual detector geometry parameters (unequal gamma angles), the system achieves accurate data conversion without introducing ring artifacts, thus resolving the contradiction between reconstruction accuracy and artifact generation.
Solution Approach 2:
The patent introduces an intermediate geometric model that bridges the fan beam geometry and parallel beam geometry specifically for unequal gamma angle configurations. This intermediary model serves as a mediator that correctly transforms fan beam projection data to parallel beam projection data while preserving the unique geometric characteristics of flat module detectors, preventing the generation of ring artifacts.
2Ease of manufacture
If traditional rebinning algorithms based on equal gamma angle geometry are applied to flat module detector arrays, then data conversion is attempted, but incorrect rebinning results are obtained leading to severe ring artifacts
Solution Approach 1:
The patent modifies the rebinning parameters to match the actual unequal gamma angle geometry of flat module detector arrays. By updating the geometric parameters in the rebinning equations to reflect the true detector configuration, the system maintains manufacturing simplicity while achieving precise rebinning results without ring artifacts.
Solution Approach 2:
The patent explicitly accounts for the asymmetric nature of unequal gamma angles in flat module detector arrays by incorporating these asymmetries into the rebinning model. Rather than forcing a symmetric equal gamma angle model, the solution embraces the asymmetric geometry, leading to accurate rebinning that preserves the cost advantages of flat module construction.
3Productivity
If fan beam data is converted to parallel beam data without proper geometric correction, then reconstruction can proceed, but distance weight causes zebra or banding artifacts across Z direction
Solution Approach 1:
The patent adjusts the geometric parameters in the rebinning process to correctly account for the relationship between fan beam and parallel beam geometries. By using the proper geometric parameters, the conversion eliminates the need for distance weighting that causes zebra or banding artifacts, enabling efficient reconstruction without these harmful artifacts.
Data Source
AI summary
A method and apparatus for data conversion in an unequal γ angle CT system. The method for imaging in a CT system having a flat module detector array includes obtaining fan beam projection data of an object from a CT scan, obtaining a geometric structure parameter of the flat module detector array; rebinning data from the fan beam projection data to parallel beam projection data based on the geometric structure parameter to convert the fan beam projection data into the parallel beam projection data, and generating a CT image from the parallel beam projection data.