Compact Open MRI Magnet with Active Shimming
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Solution Overview
Problem
Current open whole-body MRI systems require large, heavy, and costly magnets to maintain uniform magnetic fields, limiting patient access and increasing system size, weight, and operational costs, while also being less efficient in handling magnetic field drifts due to temperature variations.
Innovation Solution
A compact magnetic field generating apparatus with a cylindrical central homogeneous field region and annular protrusions on the magnet pole faces, combined with active and passive shimming techniques using spherical harmonic current coils to achieve high field uniformity, reducing the size and weight of the magnet system while maintaining imaging quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If large magnets are used to maintain uniform magnetic fields in open whole-body MRI systems, then field uniformity is improved, but system size, weight, and cost increase
Solution Approach 1:
The magnet system is divided into multiple discrete magnet blocks arranged in an open configuration. These segmented magnets work together to generate the required magnetic field while reducing the overall size and weight compared to a single large magnet, while maintaining field uniformity through optimized placement and configuration of the individual blocks
Solution Approach 2:
The patent transitions from a traditional enclosed magnet design to an open magnet configuration where magnets are arranged in a specific three-dimensional pattern with gaps. This dimensional reorganization allows the magnetic fields to combine constructively in the imaging region while reducing material usage and system weight, achieving field uniformity without requiring a solid large magnet structure
2Manufacturing precision
If large magnets are used to maintain uniform magnetic fields, then field uniformity is improved, but system cost increases
Solution Approach 1:
By segmenting the magnet system into multiple smaller blocks, the patent reduces the total amount of expensive magnetic material required. The segmented design allows for more efficient use of magnetic material while achieving the same field uniformity, thereby reducing system cost without compromising performance
Solution Approach 2:
The patent optimizes parameters such as magnet block size, spacing, and arrangement to achieve field uniformity with reduced material volume. By carefully controlling these geometric parameters, the system achieves the required field quality with smaller, less expensive magnets compared to traditional designs
3Power
If large magnets are used in open MRI systems, then field strength is maintained, but patient access is limited
Solution Approach 1:
The open magnet configuration creates vertical and lateral openings in the magnet structure, allowing patients to be positioned within the imaging region without requiring them to fit through a narrow bore. This dimensional reorganization maintains field strength while dramatically improving patient access and comfort
4Manufacturing precision
If traditional magnet designs are used, then field uniformity is achieved, but system size increases
Solution Approach 1:
The segmented magnet design concentrates the magnetic field-generating capability into compact, strategically positioned blocks rather than requiring a large continuous structure. This segmentation allows the system to achieve the same field uniformity in a reduced volume by optimizing the spatial distribution of magnetic material
Solution Approach 2:
The patent optimizes geometric parameters including magnet block dimensions, spacing between blocks, and arrangement configuration to minimize the overall system volume while maintaining field uniformity. These parameter optimizations enable a compact design that achieves the required performance with significantly reduced magnet volume
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 achieves a significant reduction in magnet size, weight, and cost by more than 50%, while maintaining less than 10 ppm overall variation in the magnetic field, improving patient access and system efficiency, and allowing for whole-body scanning with reduced power requirements.
Implementation Method 1
electrical active means to homogenize the field within the gap
Implementation Method 2
permanent magnets magnetically connected by a yoke to generate a magnetic field in the gap
Data Source
AI summary
A compact whole-body open circular magnet system for MRI purposes includes a protrusion overhanging the central homogeneous field region. The overhanging protrusion permits a reduction of the total magnet homogeneity requirements of the MRI system. Further reducing the radius of this protrusion increases access to a patient under examination but diminishes the homogeneity. Active shimming means incorporated in a gradient coil can regain the original homogeneity while maintaining increased patient access.