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A high-field superferric NMR magnet
F R Huson1, R N Bryan, W W MacKay
1Texas Accelerator Center, The Woodlands.
Magnetic Resonance in Medicine
|January 1, 1993
Summary
This study presents a novel shielding solution for 4-Tesla (4-T) magnetic resonance imaging magnets, significantly reducing problematic fringe fields. The new design uses integrated superconducting coils and saturated iron, enhancing safety and efficiency for advanced imaging applications.
Area of Science:
- Medical Physics
- Biomedical Engineering
- Materials Science
Background:
- Strong magnetic fringe fields from 4-Tesla (4-T) whole-body research magnets pose significant safety and operational challenges.
- Existing solutions like restricted zones or unsaturated iron shielding are often impractical or inefficient.
Purpose of the Study:
- To develop and validate a novel magnetic shielding method for 4-T MRI magnets.
- To contain fringe fields effectively and improve magnet efficiency.
Main Methods:
- Designed and constructed a prototype 4-T, 30-cm-bore magnet incorporating superconducting coils integrated with fully saturated iron elements.
- Tested the prototype to measure fringe field containment and magnetic field homogeneity.
Main Results:
- The prototype successfully contained the 5 Gauss fringe field within 1 meter of the magnet bore along the z-axis.
- Achieved 10 ppm magnetic field homogeneity over 30% of the magnet's diameter after passive shimming.
- Required 20% less superconductor compared to an unshielded magnet.
Conclusions:
- The integrated superconducting coil and saturated iron shielding design is a viable solution for mitigating fringe fields in 4-T MRI magnets.
- This approach enhances magnet safety, reduces material requirements, and demonstrates potential for advanced magnetic resonance imaging and spectroscopy.