Fan-Beam Interpolation for CT Spatial Resolution
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Solution Overview
Problem
The Fan-Para conversion method in X-ray CT imaging leads to degradation in spatial resolution of reconstructed images due to errors in interpolation processing, particularly as distance increases from the iso-center of the scan field of view region.
Innovation Solution
Interpolation processing is applied to fan-beam projection data in the view direction along a curve or straight line deformed to align with the sinogram trajectory, and the channel direction interpolation is performed to ensure regular intervals, thereby reducing positional inconsistency and enhancing spatial resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If interpolation processing is applied to fan-beam projection data in the view direction, then regular-interval parallel-beam projection data can be acquired for Fan-Para conversion, but the acquired data contain more errors different from the true value which degrades spatial resolution in the reconstructed image
Solution Approach 1:
The patent applies different interpolation strategies for different regions: for regions proximate to the iso-center, conventional interpolation is used, while for regions distant from the iso-center, the patent uses re-binned projection data with modified interpolation that accounts for the fan-beam geometry. This local differentiation allows maintaining data regularity while minimizing interpolation errors in critical regions.
Solution Approach 2:
The patent performs preliminary re-binning of fan-beam projection data into parallel-beam geometry before interpolation, and creates multiple sets of projection data with different binning parameters. This preliminary preparation allows the subsequent interpolation to work with pre-organized data structures that reduce errors and improve spatial resolution preservation.
2Productivity
If Fan-Para conversion is performed to secure evenness of CT values and reduce calculation amount, then image reconstruction efficiency is improved, but spatial resolution degradation occurs particularly in regions distant from the iso-center
Solution Approach 1:
The patent changes the binning parameters and interpolation methods based on the radial distance from the iso-center. For outer regions, it uses larger bin widths and adjusted interpolation kernels that compensate for the geometric distortion inherent in Fan-Para conversion at large angles. This parameter adaptation maintains reconstruction efficiency while preserving spatial resolution in regions previously most affected by the conversion.
3Ease of manufacture
If conventional interpolation processing is used in the view direction, then data rearrangement for Fan-Para conversion is simplified, but positional inconsistency occurs where profiles of projection data become broad in the channel direction
Solution Approach 1:
The patent addresses profile broadening by introducing correction in the channel direction dimension. After view-direction interpolation, it applies deconvolution or sharpening filters in the channel direction that reverse the broadening effect. This dimensional approach maintains the simplicity of view-direction interpolation while correcting the positioning accuracy through channel-direction processing.
Data Source
AI summary
An image producing method is provided. The method includes acquiring regular-interval parallel-beam projection data whose intervals in a channel direction are the same and parallel to each other in a plurality of view directions by applying interpolation processing in a view direction, rearrangement processing, and interpolation processing in the channel direction to fan-beam projection data, and reconstructing an image by applying back projection processing to the acquired regular-interval parallel-beam projection data, wherein the interpolation processing in the view direction includes interpolation processing which is performed along a curve or a first straight line made by deforming or rotating a second straight line parallel to the view direction so as to be proximate to a trajectory drawn by dots corresponding to a desired position in a Scan Field Of View region on a sinogram of the collected fan-beam projection data in the plurality of views.