Superconducting Magnet Design for Compact MRI
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Solution Overview
Problem
Current MRI systems, particularly those for extremity imaging, face challenges in producing strong, homogeneous magnetic fields in a compact size, leading to low field strengths, longer image acquisition times, and increased costs due to size and infrastructure requirements, while also posing claustrophobic discomfort for patients.
Innovation Solution
A superconducting magnet design with a primary coil structure comprising multiple coils along an axis, including a central coil of extended length, and a shielding coil structure, optimized for reduced length and increased homogeneity, using force balancing to minimize support needs and peak magnetic fields, allowing for efficient cooling and cost-effective construction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional MRI magnets are used with standard size requirements, then homogeneous magnetic fields can be produced, but the system becomes too large and expensive with increased infrastructure requirements
Solution Approach 1:
The magnet is divided into multiple discrete coil segments (first coil, second coil, third coil, fourth coil) arranged along the bore axis. Each coil segment can be independently controlled and positioned to create the desired magnetic field distribution in a compact configuration, resolving the contradiction between achieving field homogeneity and reducing overall magnet size.
Solution Approach 2:
Different coil segments are assigned different numbers of windings and positions along the bore axis to create non-uniform current distributions that compensate for field variations. The first and second coils have different winding counts than the third and fourth coils, allowing localized optimization of magnetic field properties in different regions of the bore.
2Length of stationary object
If the magnet size is reduced for extremity imaging, then patient comfort improves and costs decrease, but field strength and homogeneity deteriorate
Solution Approach 1:
The system uses dynamic control of multiple coil segments with independent current regulation. By adjusting the current magnitude and phase in each coil segment, the magnetic field distribution can be optimized in real-time for compact geometries, maintaining field homogeneity despite reduced overall magnet size.
Solution Approach 2:
The patent varies key parameters including the number of windings in different coil segments, the spacing between coils, and the current density distribution. These parameter optimizations allow compact magnet designs to achieve the same field homogeneity as larger conventional magnets.
3Manufacturing precision
If multiple coil segments are used to improve field homogeneity, then magnetic field quality improves, but device complexity increases
Solution Approach 1:
Each coil segment serves multiple functions: generating magnetic field, providing field homogeneity compensation, and enabling gradient functionality. The same physical structure performs multiple purposes, reducing the need for separate components and thereby limiting the increase in device complexity despite using multiple 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 design achieves a strong, substantially homogeneous magnetic field over a large imaging region with reduced size and stray fields, enabling efficient and cost-effective extremity MRI imaging while minimizing patient discomfort and infrastructure costs.
Implementation Method 1
A superconducting magnet design with a primary coil structure comprising multiple coils along an axis, including a central coil of extended length
Implementation Method 2
a shielding coil structure, optimized for reduced length and increased homogeneity
Data Source
AI summary
A magnetic resonance system uses a shielded superconducting magnet to produce a dsv useful for specialist imaging in an overall short magnet system at field strengths 1.5 Tesla and above. The magnet includes at least a first central coil C1, which has a length of at least 25% of the overall length of the magnet, and is used in concert with a series of symmetric primary coils, at least one set of which carry current in a direction opposite to that of the central coil. Force balancing is advantageously used in the design of the coils. The primary coils are shielded by at least one shielding coil, which carries current in a direction opposite to the majority of the primary coils. The magnet resonance system can be used for orthopedic imaging.