MRI Magnet Homogeneity via 3D Vector Optimization
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Solution Overview
Problem
Current methods for designing permanent magnets, particularly for MRI scanners, face challenges in optimizing the static magnetic field homogeneity when transitioning from a two-dimensional model to a three-dimensional shape, leading to aberrations and inhomogeneities due to finite axial extension, which are costly and time-consuming to correct.
Innovation Solution
A method that modifies the magnetization direction of individual magnetized elements in the three-dimensional model by rotating the magnetization vectors in the section plane perpendicular to the axial extension, using optimization algorithms like genetic algorithms to minimize differences in the static magnetic field characteristics between the two-dimensional and three-dimensional models, while maintaining or improving homogeneity and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a two-dimensional model is used for designing permanent magnets, then the design process is simplified and faster, but the magnetic field homogeneity deteriorates when transitioning to three-dimensional shape
Solution Approach 1:
The invention transitions from a two-dimensional design model to a three-dimensional model by adding the axial dimension. The method calculates magnetization directions in 3D space, taking into account the finite axial extension of the magnet. This dimensional expansion allows the design to account for edge effects and field distortions that occur in the axial direction, thereby maintaining magnetic field homogeneity while preserving the efficiency of computational design methods.
Solution Approach 2:
The invention modifies the magnetization direction parameters of individual magnetized elements based on their position in the three-dimensional structure. By calculating and adjusting the magnetization vectors in 3D space, the method compensates for field distortions caused by the finite axial length. This parameter optimization ensures that the magnetic field maintains the desired homogeneity characteristics throughout the bore, resolving the contradiction between design simplicity and field quality.
2Manufacturing precision
If ferromagnetic materials are inserted to compensate for field distortions, then magnetic field homogeneity is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The invention optimizes the magnetization direction parameters of the existing magnetized elements to compensate for field distortions. By adjusting the orientation and magnitude of magnetization vectors in three-dimensional space, the method achieves field homogeneity without adding external ferromagnetic materials. This parameter-based compensation simplifies the overall device structure while maintaining the desired magnetic field characteristics.
Solution Approach 2:
The magnetized elements themselves serve the dual function of generating the magnetic field and compensating for field distortions. By optimizing their magnetization directions in the three-dimensional model, the elements self-correct for edge effects and finite length distortions. This eliminates the need for separate ferromagnetic compensation materials, reducing device complexity and manufacturing cost while achieving the desired field homogeneity.
3Manufacturing precision
If the axial extension of the magnet is increased, then magnetic field homogeneity is improved, but the magnet size and weight increase
Solution Approach 1:
The invention optimizes the magnetization direction parameters of individual elements to compensate for the effects of finite axial extension. By calculating and adjusting the magnetization vectors in three-dimensional space, the method achieves field homogeneity equivalent to longer magnets without actually increasing the axial dimension. This allows compact magnet designs to achieve the same field quality as larger magnets, reducing size and weight while maintaining performance.
Solution Approach 2:
The invention addresses the axial dimension limitations by implementing a comprehensive three-dimensional magnetization optimization approach. Rather than simply extending the axial length, the method uses 3D magnetization vector calculations to compensate for the effects of finite axial extension. This dimensional approach allows the magnet to achieve homogeneous field characteristics without increasing physical size, resolving the contradiction between compact dimensions and field homogeneity.
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 allows for a more precise and cost-effective optimization of the static magnetic field in three-dimensional permanent magnets, significantly reducing aberrations and inhomogeneities, and achieving better or equal performance compared to traditional techniques.
Implementation Method 1
the magnetization of each element made of magnetized material having a predetermined direction in the plane perpendicular to the longitudinal axis of the tubular wall and said directions being defined such to generate a uniform static magnetic field
Data Source
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AI summary
Method for making magnets for use in MRI scanners, which magnets are three-dimensional and have a tubular wall made of magnetized material, the tubular wall being composed of individual elements made of magnetized material. The invention provides the following steps: determining the modulus and direction of the magnetization of elements necessary for generating a predetermined magnetic field in the cavity inside said tubular wall in a theoretical two-dimensional magnet model, extruding the two-dimensional model to a three-dimensional model and at least partially compensating aberrations, distortions or inhomogeneites of the magnetic field generated in the three-dimensional model by modifying the magnetization orientation in the individual elements and in the plane of the two-dimensional model such to minimize differences between the magnetic field in the two-dimensional model and the magnetic field in the three-dimensional model.