title: Finite element analysis of gradient z-coil induced eddy currents in a permanent MRI magnet.
abstract: In permanent magnetic resonance imaging (MRI) systems, pulsed gradient fields induce strong eddy currents in the conducting structures of the magnet body. The gradient field for image encoding is perturbed by these eddy currents leading to MR image distortions. This paper presents a comprehensive finite element (FE) analysis of the eddy current generation in the magnet conductors. In the proposed FE model, the hysteretic characteristics of ferromagnetic materials are considered and a scalar Preisach hysteresis model is employed. The developed FE model was applied to study gradient z-coil induced eddy currents in a 0.5 T permanent MRI device. The simulation results demonstrate that the approach could be effectively used to investigate eddy current problems involving ferromagnetic materials. With the knowledge gained from this eddy current model, our next step is to design a passive magnet structure and active gradient coils to reduce the eddy current effects.
authors.affiliation: Department of Biomedical Engineering, Zhejiang University, Hangzhou 310027, China. xialing@zju.edu.cn
authors.forename: Xia
authors.initials: X
authors.lastname: Li
authors.forename: Ling
authors.initials: L
authors.lastname: Xia
authors.forename: Wufan
authors.initials: W
authors.lastname: Chen
authors.forename: Feng
authors.initials: F
authors.lastname: Liu
authors.forename: Stuart
authors.initials: S
authors.lastname: Crozier
authors.forename: Dexin
authors.initials: D
authors.lastname: Xie
mesh_terms: D003198:Computer Simulation; D017076:Computer-Aided Design; D004574:Electromagnetic Fields; D004867:Equipment Design; D019544:Equipment Failure Analysis; D020342:Finite Element Analysis; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008280:Magnetics / Q000295:instrumentation*; D008962:Models, Theoretical