Segmented Permanent Magnet Assembly for Homogeneous Low-Field MRI
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Solution Overview
Problem
Conventional magnetic resonance imaging (MRI) systems, especially low-field systems, face challenges in achieving homogeneous magnetic fields and reducing manufacturing complexity and cost, particularly when using permanent magnet assemblies with non-ferromagnetic frames, as they often require continuous magnetization orientation which is difficult to achieve in practice.
Innovation Solution
The development of permanent magnet assemblies with a non-ferromagnetic frame that includes identically-shaped magnet segments with tailored magnetic orientations and features like cut-outs for patient accommodation, allowing for improved field homogeneity and reduced weight, using a combination of ferromagnetic and non-ferromagnetic segments arranged to form a bore, and employing computational optimization for segment layouts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If permanent magnet assemblies with non-ferromagnetic frames are used, then weight is reduced and portability is improved, but manufacturing complexity increases due to requirements for continuous magnetization orientation
Solution Approach 1:
The permanent magnet assembly is divided into multiple discrete magnet segments arranged in specific patterns around the bore. Each segment can be manufactured separately with standardized magnetization orientations, then assembled into the final configuration. This segmentation allows the system to achieve homogeneous magnetic fields without requiring continuous magnetization orientation across large structures, thereby reducing manufacturing complexity while maintaining the weight benefits of non-ferromagnetic frames.
Solution Approach 2:
Different regions of the magnet assembly use segments with locally optimized magnetization orientations and configurations. Computational design determines the specific arrangement and orientation of each segment to achieve homogeneous field distribution. This local optimization approach replaces the need for continuous magnetization orientation while maintaining field homogeneity, resolving the contradiction between weight reduction and manufacturing complexity.
2Ease of manufacture
If permanent magnet assemblies with non-ferromagnetic frames are used, then manufacturing cost is reduced, but achieving homogeneous magnetic fields becomes more difficult
Solution Approach 1:
Computational optimization is performed during the design phase to determine the optimal arrangement, size, and magnetization orientation of each magnet segment before manufacturing. This preliminary computational design ensures that the assembled structure will produce homogeneous magnetic fields, eliminating the need for complex precision requirements during actual manufacturing and assembly. The computational model predicts and optimizes field homogeneity, making the manufacturing process more cost-effective while maintaining precision requirements.
Solution Approach 2:
The design optimizes various parameters including segment dimensions, spacing, magnetization strength, and orientation angles to achieve homogeneous magnetic fields. By carefully adjusting these parameters through computational design, the system achieves field homogeneity using simpler, more cost-effective manufacturing processes with non-ferromagnetic frames, resolving the contradiction between manufacturing ease and field homogeneity.
3Power
If ferromagnetic segments are used in the magnet assembly, then magnetic field strength is improved, but weight increases and portability decreases
Solution Approach 1:
The magnet assembly uses composite structures combining ferromagnetic segments for field strength enhancement with non-ferromagnetic structural components for weight reduction. The ferromagnetic segments are strategically positioned where they provide maximum magnetic field contribution, while non-ferromagnetic materials form the frame and support structures. This composite approach achieves the necessary magnetic field strength for effective imaging while maintaining reduced weight and improved portability.
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 enhances magnetic field homogeneity, reduces manufacturing complexity and cost, and allows for a lighter, more portable MRI system while maintaining effective imaging capabilities.
Implementation Method 1
The first rod comprises: ferromagnetic segments, each having a net magnetization in a plane that is substantially perpendicular to the common longitudinal direction
Data Source
AI summary
An assembly for providing a B0 magnetic field for a magnetic resonance imaging (MRI) system, the assembly comprising: a plurality of rods extending along a common longitudinal direction and positioned to form a bore extending along the common longitudinal direction, the plurality of rods including a first rod, the first rod comprising: ferromagnetic segments, each having a net magnetization in a plane that is substantially perpendicular to the common longitudinal direction; and non-ferromagnetic segments.