Three-dimensional optimal shape design of magnetic pole in permanent magnet assembly for MRI taking account of eddy currents due to gradient coil field

The ferromagnetic pole pieces of permanent magnet assembly for magnetic resonance imaging is optimally designed taking account of the pulse excited gradient coil field. In the design, the transient design sensitivity analysis is combined with the three-dimensional finite element method to give a search direction. The effects of the eddy currents, induced on the ferromagnetic pole pieces, on the main magnetic-field strength and homogeneity in diameter of interested region are also investigated.