Mobile Permanent Magnet Arrangement for Open MRI
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Solution Overview
Problem
Existing MRI systems using permanent magnets face challenges such as high maintenance costs, claustrophobic patient conditions due to fixed and large magnet arrangements, and the need for a more flexible and lightweight design that allows for adjustable active volumes.
Innovation Solution
A mobile permanent magnet arrangement with a ferromagnetic facing plate and an air gap, featuring a central circular magnet and annular magnets, held by a C- or U-shaped yoke, allowing for precise movement and positioning to create a homogeneous magnetic field within an open structure, supplemented by shim assemblies and gradient coils for enhanced field homogeneity and adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If permanent magnets are permanently positioned in fixed arrangements, then the magnetic field structure is stable and simple, but the active volume cannot be adjusted and the system becomes large and unwieldy
Solution Approach 1:
The patent applies the dynamics principle by making the permanent magnet assembly mobile rather than fixed. The magnet assembly can be moved along the longitudinal axis and laterally positioned to define different active volumes. This dynamic positioning capability allows the system to adapt to different imaging requirements while maintaining a relatively simple overall structure, resolving the contradiction between adaptability and device complexity.
2Power
If large permanent magnet arrangements are used, then sufficient magnetic field strength is achieved, but the system becomes unwieldy and difficult to position
Solution Approach 1:
The patent applies segmentation by dividing the magnet system into a mobile permanent magnet assembly and a separate facing plate. This segmentation allows the magnet assembly to be optimized for magnetic field strength while being independently movable, improving positioning ease. The facing plate remains stationary providing structural support, while the magnet assembly can be precisely positioned to achieve the required field strength without making the entire system unwieldy.
3Device complexity
If fixed magnet arrangements are used, then the structure is simple, but the patient experiences claustrophobia due to enclosed spaces
Solution Approach 1:
The mobile permanent magnet assembly allows the system to create an open MRI configuration rather than a fixed enclosed bore. The magnet can be positioned to define the active volume in an open space, eliminating the claustrophobic enclosed environment while maintaining structural simplicity through the straightforward permanent magnet design. This dynamic positioning enables open architecture without requiring complex additional structures.
4Adaptability or versatility
If mobile permanent magnet assembly is used, then active volume can be defined by user and structure is open, but achieving sufficient field homogeneity becomes more difficult
Solution Approach 1:
The patent replaces complex mechanical field-shaping structures with a mobile permanent magnet assembly that achieves field homogeneity through controlled positioning. By using the mobility of the magnet assembly to precisely position the magnets relative to the facing plate and object, the system achieves sufficient field homogeneity without requiring complex mechanical field-shaping components. This substitution of positioning control for mechanical design enables user-defined active volumes while maintaining field quality.
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
Enables flexible and lightweight MRI scanning in an open environment with precise control over the magnetic field, reducing maintenance costs and alleviating patient anxiety by allowing the active volume to be defined by the user, while maintaining sufficient field homogeneity for effective MRI imaging.
Implementation Method 1
permanent magnet grouping comprising: a central permanent magnet of substantially circular cross-section; at least one permanent magnet of substantially annular cross-section arranged substantially concentrically with respect to the central permanent magnet
Implementation Method 2
a facing plate constructed from ferromagnetic material
Data Source
AI summary
The present invention provides a permanent magnet arrangement, comprising: a. a mobile permanent magnet grouping; b. a facing plate constructed from ferromagnetic material; c. a an air gap defined by the spacing between said permanent magnet grouping and said facing plate; d. a yoke of predetermined shape formed from magnetically permeable material, said yoke holding said front surfaces of said magnets in a substantially parallel arrangement relative to said facing plate; e. means for individually moving said permanent magnets in said magnet grouping along an axis generally perpendicular to said facing plate; f. means for moving said permanent magnet grouping in a plane generally parallel to said facing plate; wherein a magnetic field within an active volume located in said air gap between said permanent magnet grouping and said facing plate is provided, said magnetic field sufficiently homogeneous for performance of MRI.