Active Resistive Shim Coil Segmentation for MRI Field Homogeneity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional MRI systems face challenges in achieving optimal magnetic field homogeneity due to the limitations of superconductive shim coils, which are inaccessible for continuous adjustment, and active resistive shim coils are restricted by series connections, limiting degrees of freedom for shimming out inhomogeneities.
Innovation Solution
The implementation of an active resistive shim coil assembly with X-shim, Y-shim, and Z-shim coils connected to separate power channels, allowing for various degrees of freedom in energizing and generating harmonics to shim out inhomogeneities, particularly suited for open MRI systems with a gap between magnet halves.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If superconductive shim coils are used, then magnetic field homogeneity is improved, but accessibility for continuous adjustment is lost
Solution Approach 1:
The shim coil assembly is segmented into multiple independent resistive shim coils (X-shim, Y-shim, Z-shim coils with multiple quadrants each), allowing individual adjustment of each segment through separate power channels while collectively achieving field homogeneity correction
Solution Approach 2:
The patent replaces superconductive shim coils with resistive shim coils, substituting a mechanically inaccessible system with one that is electrically accessible and continuously adjustable through power channels during imaging
2Ease of operation
If active resistive shim coils are used with series connections, then ease of adjustment is improved, but degrees of freedom for shimming is reduced
Solution Approach 1:
Each shim coil is divided into multiple quadrants (e.g., four quadrants per X-shim and Y-shim coils, two halves per Z-shim coil), with each quadrant independently connectable to separate power channels, providing 6-10 degrees of freedom for shimming adjustments
Solution Approach 2:
The patent implements dynamic configurability where quadrants can be connected in series or parallel through switches, allowing the system to adapt its electrical configuration based on the specific shimming requirements and available power channels
3Adaptability or versatility
If separate power channels are used for each shim coil, then degrees of freedom for shimming is improved, but device complexity increases
Solution Approach 1:
The power channels and control system are designed to serve multiple functions: they can independently control different quadrants, combine quadrants in series or parallel configurations, and adapt to various shimming scenarios, reducing the need for separate dedicated circuits for each configuration
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 configuration enables easy and continuous adjustment of shim coil currents, significantly improving imaging quality by effectively reducing magnetic field inhomogeneities, even with additional medical instruments in the imaging volume, and allows for real-time adjustments during imaging.
Implementation Method 1
an active resistive shim coil assembly with X-shim, Y-shim, and Z-shim coils connected to separate power channels, allowing for various degrees of freedom in energizing and generating harmonics to shim out inhomogeneities
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Active resistive shim coil assemblies (208) may be used in magnet- ic resonance imaging (MRI) systems to reduce in-homogeneity of the magnetic field in the imaging volume. Disclosed embodiments may be used with continuous systems, gapped cylindrical systems, or verti- cally gapped systems. Disclosed embodiments may also be used with an open MRI system and can be used with an instrument (104) placed in the gap (102) of the MRI system. An exemplary embodiment of the active resistive shim coil assembly of the present disclosure includes active resistive shim coils each operable to be energized by separate currents through a plurality of power channels. In some embodiments, the disclosed active resistive shim coil assemblies allow for various degrees of freedom to shim out field in-homogeneity.