Optimal design of mri magnets with magnetic shielding

We have been developing a novel optimal design method for a highly homogeneous superconducting coil system with magnetic shielding for Magnetic Resonance Imaging (MRI). The presented optimal design method is based on a combination of the hybrid finite - boundary element method for analysis of an axially symmetric nonlinear open boundary magnetic field problem and the mathematical programming method for solving the corresponding optimization problem. In this paper, the goal programming method and the nonlinear least squares method have been adopted. The relative merits of a combination of an active shielding and a room shielding have been investigated. The proposed design method can optimize both an MRI magnet and its magnetic shielding system simultaneously taking into account the maximum permissible intensity of stray field at a specified distance from the magnet center. Several design procedures and results of a I-tesla-magnet system are shown.