A novel strategy for achieving a low-field lightweight permanent MRI magnet system with good magnetic field homogeneity and low eddy current

Jingzhi Han; Jiangqian Guo; Peng Shen; Xiao Tong; Wenyun Yang; Ziheng Zhang; Jie Liu; Tianzhuo Yang; Yikun Fang; Shunquan Liu; Jie Zhang; Qing Xu; Jinbo Yang

arXiv · 2608.21903

A novel strategy for achieving a low-field lightweight permanent MRI magnet system with good magnetic field homogeneity and low eddy current

Jingzhi Han·Jiangqian Guo·Peng Shen·Xiao Tong·Wenyun Yang·Ziheng Zhang·Jie Liu·Tianzhuo Yang·Yikun Fang·Shunquan Liu·Jie Zhang·Qing Xu·Jinbo Yang

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Abstract

In low-field, lightweight, pole-pieceless permanent-magnet MRI systems built with sintered Nd-Fe-B or Sm-Co magnets, the rapid switching of gradient fields readily induces eddy currents in the sintered magnets, leading to image artifacts. To address this, we report for the first time a Sm-Fe-N permanent-magnet MRI system based on anisotropic Sm-Fe-N bonded magnets, whose high electrical resistivity reduces the eddy currents in the X, Y and Z directions to 0.093%, 0.172% and 2.38%, respectively, while a magnetic field inhomogeneity below 150 ppm is achieved at the boundary of a 220 mm diameter of spherical volume (DSV). Compared with sintered Nd-Fe-B and Sm-Co magnets, using Sm-Fe-N bonded magnets as the source of the static magnetic field not only suppresses eddy currents but also makes a closely tiled, densely packed magnetic-circuit layout feasible, providing a more uniform static magnetic field for the MRI system. Imaging results free of obvious geometric distortion and banding artifacts further indicate that the Sm-Fe-N magnet system delivers low eddy currents and high static magnetic field homogeneity.

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Jingzhi Han, Jiangqian Guo, Peng Shen, Xiao Tong, Wenyun Yang, Ziheng Zhang, Jie Liu, Tianzhuo Yang, Yikun Fang, Shunquan Liu, Jie Zhang, Qing Xu, Jinbo Yang. 2026-08-22. A novel strategy for achieving a low-field lightweight permanent MRI magnet system with good magnetic field homogeneity and low eddy current. https://arxiv.org/abs/2608.21903

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