Coil Block Designs With Good Homogeneity for MRI Magnets Based on SVD Eigenmode Strengths

This paper describes an improved method to determine coil block (CB) placements with good homogeneities for magnetic resonance imaging magnets. Each magnet has a main coil (MC) for strong magnetic fields in a volume of interest and a shield coil (SC) to make the magnetic fields weak outside the magn...

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Bibliographic Details
Published in:IEEE transactions on magnetics 2015-10, Vol.51 (10), p.1-13
Main Authors: Abe, Mitsushi, Shibata, Keiichiro
Format: Article
Language:English
Subjects:
Approximation
coil nlock
Coiling
Coils
Homogeneity
Magnetic fields
Magnetic moments
Magnetic noise
Magnetic resonance imaging
Magnetic shielding
Magnetism
magnetomotive force
Magnets
MRI magnet
optimization
Placement
singular value decomposition
Strength
Tuning
Winding
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Summary:This paper describes an improved method to determine coil block (CB) placements with good homogeneities for magnetic resonance imaging magnets. Each magnet has a main coil (MC) for strong magnetic fields in a volume of interest and a shield coil (SC) to make the magnetic fields weak outside the magnet. The CB placements are done in three steps and at every step, the SC magnetic moments are tuned. In step 1, approximate placements are done with axially distributed circular filament loop currents. According to the distribution, rough placements of CBs are done for the MC. In step 2, the CB cross-sectional shapes and positions are optimized to get good homogeneity with real numbers of winding turns. In step 3, the CB shapes are approximated with integer numbers of winding turns and conductor sizes, and the CB positions are tuned to get as good homogeneities as the step 1 result. In all steps, optimizations are done through truncated singular value decompositions. In steps 2 and 3, the placements are done with respect to eigenmode strengths, which are obtained in step 1. For a magnet with six MC-CBs, seven symmetric eigenmode strengths are tuned. The CB placements for magnets can be obtained with good homogeneities and integerized CB winding turns using the method.
ISSN:0018-9464
1941-0069
DOI:10.1109/TMAG.2015.2412515