X-ray CT Parameter Estimation Using Multi-Directional Likelihood Search
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Solution Overview
Problem
The current projection-based image reconstruction method for X-ray CT systems has a high calculation load due to the need for iterative searches to estimate the thickness of base materials, which increases the number of repeated calculations and is inefficient.
Innovation Solution
A method that uses a computing unit to apply a projection-based approach by setting a coordinate space with axes representing the likelihood of second parameters, performing initial searches in predetermined directions, and executing further searches along a line connecting the highest likelihood points to efficiently estimate the thickness of base materials using X-ray energy distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If iterative search methods are used to estimate the thickness of base materials in projection-based image reconstruction, then the accuracy of parameter estimation is improved, but the calculation load increases significantly
Solution Approach 1:
The patent applies preliminary action by performing a first search in a predetermined direction from a starting point to obtain a first value with the highest likelihood before conducting the main iterative search. This preliminary step positions the search closer to the optimal solution, reducing the number of iterations needed in subsequent steps and thereby decreasing the overall calculation load while maintaining estimation accuracy.
Solution Approach 2:
The patent segments the iterative search process into three distinct steps: (1) a first search in a predetermined direction to obtain a first value, (2) a second search from a different starting point or direction to obtain a second value, and (3) a third search along the line connecting the first and second values to find the final estimator. This segmentation allows each step to focus on a specific aspect of the search space, improving convergence efficiency and reducing total calculation time.
2Reliability
If multiple search methods are employed to obtain the highest likelihood estimator, then the reliability of parameter estimation is improved, but the number of repeated calculations increases
Solution Approach 1:
The patent introduces a new dimension to the search process by conducting the third search along the line connecting the first value and the second value in the parameter space. This dimensional approach efficiently explores the region between two reliable estimates, ensuring that the final highest likelihood estimator is obtained with minimal additional calculations while enhancing the reliability of the result through multi-directional verification.
3Adaptability or versatility
If the projection-based method is used to handle complex spectrum response with multiple energy information, then the ability to break down materials is improved, but the computational complexity increases
Solution Approach 1:
The patent applies preliminary action by performing a first search in a predetermined direction from a starting point to obtain a first value with the highest likelihood before conducting the main iterative search. This preliminary step positions the search closer to the optimal solution, reducing the number of iterations needed in subsequent steps and thereby decreasing the overall calculation load while maintaining estimation accuracy.
Solution Approach 2:
The patent segments the iterative search process into three distinct steps: (1) a first search in a predetermined direction to obtain a first value, (2) a second search from a different starting point or direction to obtain a second value, and (3) a third search along the line connecting the first and second values to find the final estimator. This segmentation allows each step to focus on a specific aspect of the search space, improving convergence efficiency and reducing total calculation time.
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 significantly reduces the calculation load and improves the efficiency of parameter estimation and search processes in X-ray CT systems, allowing for more accurate and rapid image reconstruction.
Implementation Method 1
detecting X-ray photon groups having continuous (non-monochromatic) energy distribution by an X-ray tube
Implementation Method 2
current mode X-ray detector, which is unable to obtain energy information, for detecting X-ray photon groups
Data Source
AI summary
An X-ray CT device and a computing unit to use a projection-based method for image reconstruction are included. The computing unit sets a coordinate space having coordinate axes of the thicknesses of base materials and likelihood the thicknesses, and then based on X-ray attenuation responses, executes: a first search to search in a direction perpendicular to a ridge direction of likelihood contours for a first estimated thickness having the highest likelihood, starting with an estimated thickness input value set in the coordinate space; a second search to search for a second estimated thickness having the highest likelihood, starting with a shifted starting point at a position shifted from the estimated thickness input value; and a third search to search on a line connecting the first estimated thickness with the second estimated thickness for the highest likelihood estimator having the highest likelihood, to obtain an estimated thickness output value.