An Improved Passive Shimming Design Method

Passive shimming technology can make the uniformity of the diameter of spherical volume (DSV) region of the magnetic resonance imaging (MRI) system meet the imaging requirements. In this article, we introduce the dichotomy method to improve the optimal target magnetic field (OTMF) algorithm, so that it can quickly get the minimum shimming sheet laying scheme under the lowest magnetic field inhomogeneity and greatly reduce the iteration time. Based on the improved OTMF algorithm by dichotomy, this article continues to study the influence of the number of shimming trays, the number of pockets in each shimming tray, the size of the shimming pieces, and the spacing between the shimming pieces on the shimming effect through the DOE test design method and the Monte Carlo simulation test method. This article gives the best shimming design scheme for a 1.5-T MRI superconducting magnet, and this scheme has been proven to reduce the inhomogeneity of the magnetic field at 20 cm DSV from 1199.2373 to 0.57 ppm. The shimming design method introduced in this article has certain guiding significance in exploring the factors affecting the passive shimming effect and shimming design.