Design and Evaluation of a Planar Single-Channel Shim Coil for a Permanent Magnetic Resonance Imaging Magnet

摘要

We propose a straightforward method of designing a planar single-channel shim coil for magnetic resonance imaging (MRI) using a narrow-gap permanent magnet. The design method is based on the superposition of the current densities produced by planar second-order shim coil elements and optimization of the coefficients used for the superposition. The magnetic field homogeneity was improved from 13 to 3.3 ppm (root mean square) in the central spherical area (diameter = 18 mm), revealing that the planar single-channel shim coil is a useful device for narrow-gap permanent MRI magnets.