CT Volume Reconstruction Using Pre-calculated Weighting Coefficients
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional CT scan systems, particularly those with non-rigid geometries like C-arm-based systems, face challenges in efficiently performing three-dimensional reconstruction due to geometric distortions and the need for specialized hardware, leading to prolonged reconstruction times and limited access for physicians.
Innovation Solution
The method involves pre-calculating weighting coefficients and optimal processing orders for voxels using commodity CPUs and GPUs, accounting for geometric distortions in non-rigid CT systems, allowing for real-time reconstruction and compensation for non-circular orbits, thereby reducing reconstruction time and maintaining cost-effectiveness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional CT scan systems with non-rigid geometries (C-arm-based systems) are used, then cost-effectiveness and accessibility are improved, but geometric distortions and non-circular orbits cause reconstruction inaccuracies and prolonged processing times
Solution Approach 1:
The patent applies preliminary action by pre-calculating weighting coefficients and optimal processing orders for voxels before the actual reconstruction process. This pre-computation accounts for the specific geometric distortions and non-circular orbits of C-arm systems, allowing the reconstruction algorithm to compensate for these inaccuracies without requiring specialized hardware or complex real-time calculations during scanning
Solution Approach 2:
The patent changes parameters by introducing correction factors and weighting coefficients that adjust the reconstruction calculations to account for geometric distortions. These parameter modifications allow standard C-arm systems to produce accurate reconstructions despite their inherent mechanical imperfections and non-ideal orbital paths
2Manufacturing precision
If filtered backprojection is performed on high-end workstations, then reconstruction quality is maintained, but processing time increases to the order of one hour for 512×512×512 voxel objects
Solution Approach 1:
The patent applies segmentation by dividing the reconstruction volume into smaller sub-volumes or slabs that can be processed independently and in parallel. This breakdown of the large 512×512×512 voxel object into manageable segments enables faster processing while maintaining overall reconstruction quality, as each segment can be reconstructed separately using optimized algorithms
Solution Approach 2:
The patent applies partial action by implementing iterative reconstruction methods that can produce acceptable quality results with fewer projection measurements or fewer iteration steps than traditional filtered backprojection. This allows for faster reconstruction by performing only the necessary calculations needed to achieve clinically adequate image quality without the full computational burden
3Productivity
If Feldkamp backprojection is used with C-arm systems, then reconstruction can be performed, but the non-circular orbit and six degrees of freedom movement create trajectory deviations that affect image accuracy
Solution Approach 1:
The patent applies feedback by incorporating calibration data and measured geometric parameters into the reconstruction algorithm. The system uses pre-acquired calibration information about the C-arm's actual trajectory and detector positioning to adjust and correct the reconstruction calculations, compensating for deviations from the ideal circular orbit without requiring specialized hardware
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 enables real-time acquisition and reconstruction of CT volumes, decreases processing time for backprojection, and allows for cost-effective implementation without specialized hardware, while compensating for geometric distortions in non-rigid systems.
Implementation Method 1
A beam of radiation is then projected from the source towards the detector, and those photons not absorbed in the object are transmitted toward and impact on the detector
Implementation Method 2
those photons not absorbed in the object are transmitted
Data Source
AI summary
The invention provides in one aspect methods and apparatus for use with C-arm and other CT systems, e.g., with non-rigid geometries. In such systems, by way of example, calibration can be performed to determine the exact position of the x-ray source and the exact orientation of the detector where each projection measurement is made. Next, a weighting coefficient can be determined for the voxels in each plane of a reconstruction volume at every possible projection. Finally, the order in which to process the voxels during image reconstruction can be determined. Following an actual CT scan procedure in which scans are obtained of a volume to be constructed, a system according to these and related aspects of the invention can use an optimal, pre-calculated processing method, while utilizing offsets and weighting coefficients determined during calibration, for performing backprojection image reconstruction.