Coil Orientation Patterns for MRI Magnet Field Homogeneity
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Solution Overview
Problem
Existing magnet assemblies in magnetic resonance examination systems face challenges in achieving high spatial uniformity of the magnetic field due to manufacturing tolerances and asymmetries in electrically conductive coils, requiring extensive shimming efforts to correct field inhomogeneities.
Innovation Solution
The magnet assembly optimizes coil orientations to minimize inherent spatial inhomogeneities by rotating the coils to specific patterns, combined with a current supply and return line-arrangement that cancels induced magnetic fields, reducing the need for extensive shimming and enhancing field homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional magnet assemblies are used with standard coil orientations, then manufacturing is simpler, but spatial field homogeneity deteriorates due to manufacturing tolerances and asymmetries
Solution Approach 1:
The patent applies asymmetry by deliberately rotating coils to non-symmetric orientations that compensate for manufacturing tolerances and asymmetries. Instead of using symmetric coil arrangements, the invention introduces specific asymmetric rotation angles for individual coils to cancel out field inhomogeneities caused by manufacturing variations, thereby improving spatial field homogeneity.
Solution Approach 2:
The patent changes the orientation parameter of coils from standard symmetric positions to optimized asymmetric angles. By adjusting the rotation angles of coils as a key parameter, the invention compensates for manufacturing tolerances and achieves better field homogeneity without requiring higher manufacturing precision.
2Manufacturing precision
If shimming elements are added to correct field inhomogeneities, then spatial field homogeneity improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the shimming function from separate physical shimming elements and integrates it into the coil orientation arrangement itself. By rotating coils to specific asymmetric angles, the invention generates compensating magnetic fields directly from the main coils, eliminating the need for additional shimming elements and reducing device complexity.
Solution Approach 2:
The patent makes the main coils serve a dual function: generating the primary magnetic field and simultaneously compensating for field inhomogeneities through asymmetric orientation. This multi-functionality eliminates the need for separate shimming elements, as the main coils perform both magnet generation and field homogenization.
3Manufacturing precision
If extensive shimming is performed to achieve high field homogeneity, then image quality improves, but examination time and processing complexity increase
Solution Approach 1:
The patent performs preliminary field homogenization by pre-rotating coils to optimized asymmetric orientations before the examination process. This preliminary action compensates for manufacturing tolerances in advance, eliminating the need for time-consuming shimming adjustments during system setup or examination preparation.
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 achieves a high degree of spatial field homogeneity, minimizing the need for shimming and improving image quality in magnetic resonance imaging systems by reducing image artifacts associated with magnetic field inhomogeneities.
Implementation Method 1
The coil-arrangement, when activated by passing an electrical current through the electrically conductive coils, generates a magnetic field
Implementation Method 2
This stationary spatially uniform main magnetic field polarizes nuclear spins in the subject to be imaged
Data Source
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AI summary
A magnet assembly comprising a coil-arrangement including multiple electrically conductive coils. A line-arrangement of a current supply line-assembly and a current return line-assembly passes an electrical current through the coil arrangement. The coils are rotationally arranged at an optimum magnetic field homogeneity of the coil-arrangement. By suitable rotation of the respective electrically conductive coils in their respective planes a minimum of the level of the magnetic field's spatial inhomogeneities as a function of the orientations of the electrically conductive coils is achieved. That is, an insight of the invention is that there exist(s) one or several combinations or relative orientations (orientation patterns) for which the spatial field inhomogeneity of the coil-arrangement as such is minimal.