Shimming Device Correction via Phase Image Symmetry Estimation
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Solution Overview
Problem
Achieving homogeneous magnetic field distribution in MRI apparatuses is challenging, especially at eccentric positions, due to the sensitivity of shimming devices to deployment accuracy, leading to suboptimal image quality in areas like the shoulder region.
Innovation Solution
A method and system for correcting the shimming device deployment by acquiring phase images of a phantom, extracting internal contour lines, mapping them to coordinate systems, and estimating symmetry to determine the optimum deployment point, which compensates for initial laser positioning errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the shimming device is positioned using laser marking, then the deployment process is simple and quick, but the positioning accuracy is insufficient to achieve optimal shimming effects
Solution Approach 1:
The patent implements a feedback mechanism by acquiring phase images at multiple test positions, extracting contour lines, mapping them to coordinate systems, and estimating symmetry to determine the optimal deployment point. This feedback loop allows the system to automatically adjust and correct positioning errors, resolving the contradiction between simple deployment and accurate positioning.
Solution Approach 2:
The patent replaces the mechanical laser marking and manual positioning system with an automated image processing and symmetry estimation system. By using phase images, contour extraction, and computational symmetry analysis, the system achieves higher positioning accuracy without complicating the deployment process.
2Reliability
If the shimming device is deployed at the center position of the magnet cross section, then the magnetic field homogeneity is improved at the center, but the shimming effects become highly sensitive to deployment accuracy at eccentric positions
Solution Approach 1:
The patent performs preliminary actions by acquiring phase images at multiple predetermined test positions before finalizing the deployment point. By pre-testing multiple positions and using symmetry estimation to identify the optimal point, the system proactively compensates for the sensitivity issue rather than reacting to errors after deployment.
Solution Approach 2:
The patent changes the parameter of evaluation from simple geometric centering to magnetic field symmetry assessment. By using phase image symmetry estimation as the criterion for optimal positioning, the system identifies the true optimal deployment point that maximizes shimming effectiveness, accounting for the sensitivity at eccentric positions.
3Reliability
If the shimming device is adjusted to achieve optimal shimming effects, then the magnetic field homogeneity is improved, but the deployment process becomes more complex and time-consuming
Solution Approach 1:
The patent implements self-service by enabling the system to automatically determine the optimal deployment point through automated image processing, contour extraction, and symmetry estimation. The system serves itself by using the acquired phase images and computational analysis to identify the optimal position without requiring manual adjustment or complex external tools, thus reducing overall process complexity.
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 allows for improved shimming effects by accurately determining the optimal deployment point of the shimming device, enhancing magnetic field homogeneity and image quality, particularly in areas with inhomogeneous field distributions.
Implementation Method 1
various types of magnetic resonance imaging (MRI) apparatus acquire molecular structures and structural information about the interior of human bodies, for example, by using nuclear magnetic resonance phenomena on the basis of the magnetic fields generated by magnets
Implementation Method 2
A shimming device (e.g., a shim shell) may be placed in the magnet of the MRI apparatus, so as to compensate for the lack of homogeneity in the main magnetic field (e.g., B0 field)
Data Source
AI summary
Disclosed in the present embodiments are a method and a device for correcting a shimming device. A phase image in a coronal plane direction of a phantom is used to make an estimation of a degree of symmetry of the phase image for each test position of the shimming device. From the image symmetry estimation result corresponding to each test position, a test position with the best image symmetry estimation result is selected to be an optimum deployment point of the shimming device.