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Z-Gradient Coil Design with Improved Anti-eddy Performance for MRI System with Opposed Permanent Magnets

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Abstract

This study introduces a method for designing the Z-gradient coil in a low-field (0.05 T) magnetic resonance imaging (MRI) system, taking into consideration the adverse effects of Z-gradient coil-induced eddy currents (gradient eddy currents). The gradient coil with a better anti-eddy performance means that it produces smaller eddy currents in the surrounding structures and thus has a smaller impact on imaging results. The electromagnetic complexity of the device makes it challenging to evaluate the impact of Z-gradient coil-induced eddy currents. To address this issue, a simplified two-dimensional model based on the finite-element method (FEM) is proposed. A multi-objective optimization method is approximately solved to get the Pareto front, considering nonlinearity, gradient efficiency, and inductance. The simulated field response and eddy losses serve as the final evaluation factors to ensure that the good anti-eddy performance. The fabricated optimal Z-gradient coil is tested and compared with a coil designed from the conventional method. Experimental eddy current response and T2-weighted image comparison show that the optimal coil has better anti-eddy performance than the conventional coil.

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Availability of Data and Materials

Data supporting this study are included within this article. For more data, please contact kong@em.ist.hokudai.ac.jp.

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Funding

This work was supported by the Japan Science and Technology Agency (JST), under Grant JPMJSP2119, National Natural Science Foundation of China, under Grant 52077023, and Shenzhen Science and Technology Innovation Commission, under Grant CJGJZD20200617102402006.

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Authors and Affiliations

  1. Hokkaido University, Sapporo, Japan

    Xiaohan Kong & Hajime Igarashi

  2. Chongqing University, Chongqing, China

    Zheng Xu

  3. Massachusetts General Hospital, Boston, USA

    Sheng Shen

  4. Shenzhen Academy of Aerospace Technology, Shenzhen, China

    Jiamin Wu & Yucheng He

Authors
  1. Xiaohan Kong
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  4. Jiamin Wu
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Contributions

XK wrote the main manuscript text; ZX and IH provided the conception and critical revision of this work; SS, JW, and YH collected data from experiments.

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Correspondence to Zheng Xu or Hajime Igarashi.

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Kong, X., Xu, Z., Shen, S. et al. Z-Gradient Coil Design with Improved Anti-eddy Performance for MRI System with Opposed Permanent Magnets. Appl Magn Reson 54, 869–890 (2023). https://doi.org/10.1007/s00723-023-01577-0

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