High Shielding Gradient Coil for Planar MRI Systems
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Solution Overview
Problem
Planar superconducting MRI systems face challenges in reducing eddy current interference due to metal structures, as traditional stray field shielding methods are inadequate for the unique magnet structure, leading to compromised imaging quality.
Innovation Solution
A method is developed to design a high shielding gradient coil by determining the outer profile of conductor structures near the gradient coil, calculating stray field distribution, partitioning the shielding area, and setting stray field strength constraints to optimize the coil design, ensuring effective stray field shielding across both planar and lateral areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional planar stray field shielding method is used, then the shielding area is limited to the planar surface of the polar plate, but the lateral side metal structures cannot be effectively shielded, leading to insufficient eddy current reduction
Solution Approach 1:
The patent extends the shielding area from traditional two-dimensional planar surface to three-dimensional space by adding lateral side shielding. The shielding area now includes both the planar surface area and the lateral side area, transforming the shielding approach from flat to volumetric, thereby effectively covering metal structures on all sides of the gradient coil.
Solution Approach 2:
The shielding area is divided into two distinct segments: planar surface area and lateral side area. Each segment is independently optimized and designed to address specific shielding needs. The total shielding effect is the combination of both segments working together to reduce eddy current interference from different directions.
2Power
If the distance between outer magnet coils is reduced to increase magnetic field efficiency, then the groove structure is formed suitable for placing gradient coils, but metal structures appear on the exterior and lateral sides of the gradient coil, worsening the stray field shielding problem
Solution Approach 1:
Different regions around the gradient coil are provided with differentiated shielding qualities. The planar surface area and lateral side area are both equipped with shielding structures, but with different geometries and orientations. Each local region receives tailored shielding appropriate to its specific exposure to stray fields, optimizing the overall shielding effectiveness.
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
The method achieves a significant reduction in stray field interference, enhancing imaging quality by fully shielding the gradient coil from stray fields, including both planar and lateral areas, thereby improving the stability and efficiency of the magnetic field.
Implementation Method 1
When the gradient magnetic field is switching, eddy currents will be generated on the surrounding metal structures
Implementation Method 2
eddy currents will be generated on the surrounding metal structures, and the secondary magnetic fields generated by the eddy currents in the imaging area
Data Source
AI summary
The present application provides a method of designing a high shielding gradient coil for a planar superconducting magnetic resonance imaging (MRI) system and a gradient coil thereof, the method determines a shielding area according to an outer profile of a metal conductor around the position of the gradient coil in the planar superconducting MRI system, and performs partitioned shielding of a stray field. The constraint values of stray fields at different partitioned zones of the shielding area are adjusted according to the shielding requirements. The primary coils of both the transverse gradient coil and the longitudinal gradient coil optimized by the design method of the high shielding gradient coil contain a reverse coil, which generates a magnetic field that offsets leakage magnetic field of other coils, thus achieving the purpose of reducing the stray field of the gradient coil.