Design and Optimization of Superconducting MRI Magnet Systems With Magnetic Materials

Abstract—We present a method for the optimal design of su-perconducting magnet systems for magnetic resonance imaging (MRI). The method integrates a linear-programming technique with the finite-element method (FEM) to calculate minimum-volume coil configurations subject to magnetic field homogeneity constraints for MRI systems that contain general nonaxisymmet-ric magnetic yoke structures. The method rapidly converges and only requires a small number of iterations and FEM analyses to be performed. In particular, the method is well suited for magnet design problems that necessitate large 3-D FEM models. We demonstrate the method with the optimal design of an open and compact 0.5 T yoked biplanar magnet assembly considered for use in an integrated medical linear accelerator and MRI system. In particular, the coil configuration for this magnet design is con-structed from a MgB2 high-temperature superconducting mater-ial that operates in a conduction-cooled cryogen-free environment. Index Terms—Image-guided radiation therapy, magnet design, magnetic resonance imaging (MRI), optimization, superconduct-ing magnets. I