MRI Shimming Circuitry for Multi-Slice Field Homogeneity
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Solution Overview
Problem
Current magnetic resonance imaging (MRI) systems face challenges in accurately stabilizing and rapidly switching correction magnetic fields for second-order shimming during multi-slice imaging, leading to incomplete correction of static magnetic field inhomogeneities.
Innovation Solution
The MRI apparatus calculates and applies 0-order, first-order, and second-order shimming values across the entire collection region, using a distribution of the static magnetic field to stabilize the correction magnetic field generated by the shim coil, allowing for improved correction of higher-order components uniformly across all slices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If second-order shimming values are used in per-slice static magnetic field shimming, then correction accuracy of static magnetic field inhomogeneity is improved, but the time required to stabilize the correction magnetic field increases
Solution Approach 1:
The system performs preliminary calculation of second-order shimming values for all slices before actual imaging acquisition. This allows the correction magnetic field to be pre-stabilized, eliminating the time delay that would normally occur during the imaging process when switching between slices.
Solution Approach 2:
The system dynamically adjusts the correction magnetic field based on pre-calculated second-order shimming values, allowing rapid switching between slices while maintaining field stability. The shim coil currents are optimized to achieve both high correction accuracy and fast switching performance.
2Stability of the object's composition
If second-order shimming values are applied during multi-slice imaging, then uniformity of correction across all slices is improved, but the speed of switching correction magnetic field between slices deteriorates
Solution Approach 1:
Second-order shimming values for all slices are calculated in advance before imaging begins. This preliminary calculation allows the system to establish uniform correction parameters across all slices upfront, eliminating the need for time-consuming recalculation or adjustment during slice transitions.
Solution Approach 2:
The system changes the shimming parameters by incorporating second-order terms in the cost function minimization. This mathematical approach allows uniform correction across all slices while maintaining the ability to rapidly switch between slices by simply adjusting coil currents based on pre-determined parameters.
3Productivity
If per-slice static magnetic field shimming is performed with only 0-order and first-order components, then processing speed is maintained, but correction completeness of higher-order inhomogeneities deteriorates
Solution Approach 1:
The system performs preliminary calculation of second-order shimming values for all slices before actual imaging acquisition. This allows the correction magnetic field to be pre-stabilized, eliminating the time delay that would normally occur during the imaging process when switching between slices.
Solution Approach 2:
The system dynamically adjusts the correction magnetic field based on pre-calculated second-order shimming values, allowing rapid switching between slices while maintaining field stability. The shim coil currents are optimized to achieve both high correction accuracy and fast switching performance.
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 enhances the accuracy and efficiency of static magnetic field shimming, improving image quality by uniformly correcting static magnetic field inhomogeneities across all slices during multi-slice imaging.
Implementation Method 1
a shim coil 101 that generates a correction magnetic field for correcting inhomogeneity of a static magnetic field in a collection region
Implementation Method 2
a static field magnet 100 that generates a static magnetic field in an inner space
Data Source
AI summary
A magnetic resonance imaging apparatus includes processing circuitry calculating a 0-order shimming value for correcting 0-order components of inhomogeneity of a static magnetic field of a collection region in a multi-slice collection for each of slices in the collection region, first-order shimming values for correcting first-order components of the inhomogeneity for each of the slices in the collection region, and multiple-order shimming values for correcting second or higher-order components of the inhomogeneity over the entire of the collection region, by using a distribution of the static magnetic field in the collection region, and imaging control circuitry performing the multi-slice collection to the collection region by using the 0-order, first-order, and multiple-order shimming values.