Grooved Shield Assembly for MRI Magnet-Gradient Interaction
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Solution Overview
Problem
Magnetic resonance imaging (MRI) systems face challenges in suppressing magnet-gradient interaction (MGI) due to motional eddy currents, which cause heating and quenching, especially in compact, high-performance, high-field scanners, as existing methods are costly and restrictive.
Innovation Solution
A shield assembly with a conductive layer featuring grooves is positioned between the main magnet assembly and the gradient coil assembly, allowing induced eddy currents to flow while blocking motional eddy currents, thereby reducing heating and quench risks without increasing the bore size or material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If rapid switching of strong gradient coils is used to achieve high-performance MRI imaging, then imaging quality and speed are improved, but leakage magnetic field causes induced eddy currents that generate motional eddy currents leading to heating and quench risks
Solution Approach 1:
A shield assembly is introduced as an intermediary component positioned between the gradient coils and the main magnet assembly. This shield assembly includes a conductive layer with grooves that serves as a mediator to block motional eddy currents while allowing induced eddy currents to flow, thereby protecting the main magnet from heating and quench risks without compromising imaging performance
Solution Approach 2:
The conductive layer of the shield assembly is segmented by introducing grooves that divide the continuous conductive path into separate regions. This segmentation blocks the formation of large-scale motional eddy currents while still permitting controlled induced eddy currents to flow in specific directions, thus reducing heating risks while maintaining gradient coil functionality
2Reliability
If known systems and methods are used to manage magnet-gradient interaction, then some protection is provided, but the systems are disadvantaged in cost and complexity
Solution Approach 1:
The shield assembly utilizes a thin conductive layer rather than bulky complex shielding structures. This thin film approach provides effective protection against magnet-gradient interaction while minimizing additional complexity and cost, making the system more practical for high-field MRI applications
3Volume of moving object
If compact high-field scanner design is implemented, then bore size is reduced, but motional eddy currents pose serious risk of heating and quench to the magnet
Solution Approach 1:
The shield assembly serves as a protective intermediary that enables compact high-field scanner design by blocking motional eddy currents in the confined space between gradient coils and main magnet, allowing reduced bore size without compromising magnet safety
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 solution effectively reduces motional eddy currents, minimizing heating and quench risks in high-field MRI systems, allowing for high-gradient power sequences without limiting sequence parameters, and is cost-effective by using thin conductive materials.
Implementation Method 1
Rapid switching of strong gradient coils generate leakage magnetic field, which causes induced eddy currents that in turn generate motional eddy currents
Implementation Method 2
leakage magnetic field, which causes induced eddy currents
Data Source
Figure 1
Figure 2A~2B
Figure 3A~3B
AI summary
A magnetic resonance (MR) system (10) is provided. The system includes a main magnet assembly (12) configured to generate a polarizing magnetic field, a gradient coil assembly (22) including a plurality of gradient coils configured to apply at least one gradient field to the polarizing magnetic field, and a shield assembly (208) positioned between the main magnet assembly (12) and the gradient coil assembly (22). The shield assembly (208) includes a conductive layer (304) fabricated with an electrically conductive material and defining grooves (308) positioned through the conductive layer (304), wherein the grooves (308) are configured to block motional eddy currents caused by actions of the polarizing magnetic field and the at least one gradient field when the at least one gradient field is applied.