Design optimization method for a ferromagnetically self-shield MR magnet

A method is described for designing a self-shielded MR (magnetic resonance) magnet. This method determines optimal shielding while maintaining an homogeneous imaging volume. This technique uses the finite-element method in the design iteration loop to solve the magnetic field problem, which includes nonlinear, saturable iron. From the magnetic field solution, the iron magnetization and its contribution to the bore field are determined. The positions and sizes of the current carrying coils are then optimized to obtain the best possible homogeneity. The design iterations are continued until the solutions converge. The iron shield design can also be modified at any iteration if further optimization of the iron shield is required.