MRI Magnetic Unit With Passive Shielding Rings for Stray Field Suppression
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Solution Overview
Problem
Conventional gradient coil units in MRI scanners generate stray fields and eddy currents that interfere with the superconducting coil unit, leading to quenching and reduced image quality, while active shielding requires significant space and energy, narrowing the patient intake area and increasing energy consumption.
Innovation Solution
A magnetic unit with a passive shielding unit comprising a support structure and ring structures that form a barrier between the gradient coil unit and the superconducting coil unit, using highly conductive materials to redirect and compensate for eddy currents and stray fields, thereby reducing their impact on the superconducting coil unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If active shielding with secondary coils is used, then stray fields and eddy currents are suppressed, but the patient intake area is narrowed and energy consumption increases
Solution Approach 1:
The patent extracts and eliminates the secondary coil unit from the gradient coil assembly, replacing active shielding with a passive shielding structure consisting of conductive rings. This removal of the secondary coils eliminates the space they would occupy, thereby maintaining a large patient intake area while still providing shielding functionality through the passive rings positioned between the main magnet and gradient coils
Solution Approach 2:
The patent introduces passive conductive shielding rings as intermediary elements between the main magnet and the gradient coils. These rings act as mediators that intercept and redirect stray fields and eddy currents away from the superconducting coil, providing protection without requiring active control or additional space for secondary coils
2Object-affected harmful factors
If active shielding with secondary coils is used, then stray fields and eddy currents are suppressed, but energy consumption increases
Solution Approach 1:
The patent implements self-service shielding where the passive conductive rings automatically respond to stray fields and eddy currents without requiring external control. The rings utilize their own electrical conductivity to generate opposing fields that cancel harmful effects, eliminating the need for gradient amplifiers to supply additional energy for active shielding control
Solution Approach 2:
The passive conductive rings serve as energy-efficient intermediaries that intercept and redirect electromagnetic fields without requiring powered actuators or control systems, thereby suppressing harmful fields while minimizing additional energy consumption
3Use of energy by stationary object
If the gradient coil unit operates without secondary coils, then energy consumption and patient intake area are improved, but eddy currents affect the superconducting coil unit
Solution Approach 1:
The patent positions passive conductive shielding rings as intermediary protective elements between the gradient coils and the main magnet's superconducting coil. These rings intercept eddy currents and stray fields generated by the gradient coils, preventing them from reaching and affecting the superconducting coil unit, thereby enabling gradient operation without secondary coils while maintaining protection
4Area of stationary object
If the gradient coil unit operates without secondary coils, then patient intake area is enlarged, but vortex fields negatively affect image quality
Solution Approach 1:
The passive conductive shielding rings act as intermediary structures that intercept and redirect vortex fields and stray fields before they enter the patient reception area. By positioning these rings strategically between the gradient coils and the main magnet, the patent reduces the intensity and complexity of vortex fields affecting the imaging region, thereby maintaining image quality without requiring space-consuming secondary coils
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 passive shielding effectively suppresses stray fields and eddy currents, enhancing image quality and reducing energy consumption, while allowing for a larger patient intake area and more efficient energy use.
Implementation Method 1
a superconducting coil unit (31) designed to generate a static main magnetic field
Implementation Method 2
at least two ring structures (42) which have planar contact with the support structure unit (41) perpendicular to the radial direction
Implementation Method 3
using highly conductive materials to redirect and compensate for eddy currents and stray fields
Data Source
Figure 1
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AI summary
The invention relates to a magnetic unit designed for use in a magnetic resonance device comprising a hollow cylindrical vacuum container surrounding a cylindrical patient reception area along a longitudinal axis of the cylinder, a superconducting coil unit designed for generating a static main magnetic field and arranged within the hollow cylindrical vacuum container, and a passive shielding unit comprising a support structure unit which surrounds the patient reception area in a hollow cylindrical shape, and at least two ring structures which are designed in a hollow cylindrical shape, wherein the at least two ring structures have planar contact with the support structure unit perpendicular to the radial direction and two of the at least two ring structures are spaced apart from each other in the longitudinal direction.