CT Reconstruction With Smooth Boundary Filtering for Out-of-View Regions
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Solution Overview
Problem
Conventional CT reconstruction methods fail to accurately reconstruct objects that are partially or fully outside the scanner's view cylinder, leading to missing, distorted, or blurry images due to incomplete data capture and artificial density artifacts at the view cylinder boundaries.
Innovation Solution
A computer-implemented method involving smooth filtering and augmented back-projection of CT projection images to generate smooth boundary filtered images, which includes adding smoothing pixels before and after detector pixels and reconstructing a larger volume size to include out-of-view regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional CT reconstruction is limited to within a capped cylinder view, then the reconstruction process is simple and fast, but the reconstruction is incomplete and inaccurate for objects that extend beyond the detector's field of view
Solution Approach 1:
The patent applies preliminary action by performing smooth filtering on the projection images before back-projection. This preprocessing step prepares the data in advance to eliminate discontinuities at the view cylinder boundary, ensuring that when the augmented back-projection reconstructs regions outside the conventional view cylinder, the results are accurate and free from artificial density artifacts.
Solution Approach 2:
The patent extends the reconstruction from the conventional 2D capped cylinder view into the third dimension of spatial coverage by implementing augmented back-projection. This allows reconstruction of regions that were previously out-of-view, effectively adding a dimensional aspect to the field of view without requiring additional physical detectors.
2Ease of operation
If objects are placed laterally shifted in the scanner, then the scanning process is more flexible and easier to operate, but the tomographic reconstruction becomes missing, inaccurate, and difficult to see
Solution Approach 1:
The patent changes the parameter of the filtering operation from conventional sharp filtering to smooth filtering. This parameter change in the filtering approach allows the reconstruction to tolerate lateral shifts and misalignments without producing artificial density artifacts, thereby maintaining reconstruction accuracy even when scanning flexibility is utilized.
Solution Approach 2:
The smooth filtering operation acts as an intermediary between the laterally shifted projection data and the final reconstruction. This intermediary processing step smooths out discontinuities that would otherwise cause artifacts, mediating between the flexible (but potentially misaligned) scanning process and the accurate reconstruction requirement.
3Power
If conventional sharp filtering is applied at the view cylinder boundary, then the processing is computationally efficient, but artificial density artifacts and bright regions appear at the boundary
Solution Approach 1:
The patent converts the potentially harmful effect of discontinuities at the view cylinder boundary into a benefit by applying smooth filtering. Instead of allowing sharp transitions to create artificial density artifacts, the smooth filtering transforms these discontinuities into gradual transitions, eliminating the harmful artifacts while maintaining processing efficiency.
Solution Approach 2:
The patent changes the filtering parameter from sharp to smooth, which fundamentally alters how the processing handles the view cylinder boundary. This parameter change eliminates artificial density artifacts while maintaining computational efficiency, as the smooth filtering can be implemented through standard convolution operations.
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
This approach ensures accurate reconstruction of out-of-view regions, eliminates artificial density artifacts, and enhances the quality and detail of the reconstructed images by capturing more of the scanned object, improving tolerance to lateral shifts and alignment issues.
Implementation Method 1
A computed tomography scan (CT scan) typically involves placing a physical object on a rotating platform inside a Computed Tomography scanner (CT scanner) between an x-ray source and x-ray detector
Data Source
AI summary
A computer-implemented method and system of CT reconstruction can include receiving one or more CT projection images; performing smooth filtering on the one or more CT projection images to generate one or more smooth boundary filtered images; and back-projecting the one or more smooth boundary filtered images.