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Title: An Irregular-Shaped Inward-Outward Ring-Pair Magnet Array with a Monotonic Field Gradient for 2D Head Imaging in Low-Field Portable MRI
Authors: Ren, Z.H.
Gong, J.
Huang, S.Y. 
Keywords: Current density model
genetic algorithm
homogeneous magnetic field
linear gradient field
low-field MRI
magnet array
permanent magnet array
portable MRI
spatial encoding field
Issue Date: 2019
Publisher: Institute of Electrical and Electronics Engineers Inc.
Citation: Ren, Z.H., Gong, J., Huang, S.Y. (2019). An Irregular-Shaped Inward-Outward Ring-Pair Magnet Array with a Monotonic Field Gradient for 2D Head Imaging in Low-Field Portable MRI. IEEE Access 7 : 48715-48724. ScholarBank@NUS Repository.
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
Abstract: We present a design and the optimization of an irregular-shaped inward-outward (IO) ring-pair magnet array that generates a 1D monotonic field pattern for 2D head imaging in a low-field portable magnetic resonance imaging (MRI) system. The magnet rings are discretized into fan-shaped ring segments with varying outer radii for the design and optimization. Besides, the inner radii of ring-pairs are tapered from outside in to provide the controlled field inhomogeneity. Genetic algorithm (GA) was used, and a current model for a fan-shaped ring segment was derived to have a fast forward calculation in the optimization. A monotonic field pattern is successfully obtained along the x-direction in a cylindrical field of view (FoV), with a relatively strong magnetic field (132.98 mT) and the homogeneity of 151840 ppm. The proposed array was further evaluated by applying its field as a spatial encoding magnetic field (SEM) for imaging by using simulation. Due to the field monotonicity, the reconstructed image by applying the fields of the proposed array shows clearer features (a higher structural similarity index) with a reduced error rate compared to that using a sparse dipolar Halbach array. The proposed magnet array is a promising alternative to supply SEM for imaging in a permanent-magnet-based low-field portable MRI system. © 2013 IEEE.
Source Title: IEEE Access
ISSN: 2169-3536
DOI: 10.1109/ACCESS.2019.2909834
Rights: Attribution-NonCommercial-NoDerivatives 4.0 International
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