A more accurate passive shimming design method for high field MRI

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Abstract
Linear programming is usually adopted in passive shimming design for MRI. Its main method is to optimize the thickness of the shims, whereas for high field MRI, the thickness of the shims arranged on the internal rail track is larger due to higher field deviation. In addition, the design error resulting from it cannot be ignored. To address these challenges, a hybrid technique is proposed to achieve more accurate passive shimming. First, linear programming is adopted to determine the preliminary layout of the shims in the pre-arranged space lattice and then integrate the three dimensions of the shims including the thickness by non-linear programming to determine the more accurate configuration of passive shims. Due to the slow speed of integration and iterative optimization, this paper adopts a spherical uniform sampling method with stronger representation to selectively optimize the local integral of the initial shims of linear programming. In addition, we propose an efficient multi-dimensional matrix integration method to achieve the purpose of optimization more quickly and accurately. It is found that the homogeneity designed by the proposed hybrid method is tens of ppm better than that of the previous linear programming method. The proposed hybrid passive shimming technique can efficiently achieve more accurate and better homogeneity results, which promote the development of high-end MRI systems.
Funding Information
  • Anhui University of Science and Technology (2023yjrc54 Talents Introduction Fund (13230408 the High Homogeneity))
  • Institute of Plasma Physics, Chinese Academy of Sciences (XDB25000000)

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