Simulation and Optimization of a Permanent Magnet for Small-Sized MRI by Genetic Algorithm

The main magnet produces the main magnetic field in the imaging area as one of the important parts of the magnetic resonance imaging (MRI) system. In a permanent MRI magnet, the widespread end effect causes a non-uniform magnetic field distribution and affects the imaging quality. In this paper, an H-type permanent magnet for small-sized MRI applications was designed; in particular, we added an optimized shimming ring outside the pole piece to improve the magnetic field uniformity. Genetic algorithms are used to solve the complex and nonlinear calculation of the magnetic field. The simulation results show that the magnet optimized by the proposed method generates a homogeneous magnetic field that can be easily implemented in practice.