Minimum Volume Optimal Design Method of Hybrid MRI Magnet

The purpose of this paper is to present a minimum volume optimal design method of hybrid magnetic resonance imaging (MRI) magnet using field superposition. The hybrid MRI magnet made by high-temperature superconductor (HTS) and low-temperature superconductor (LTS) is the optimal approach of producing higher magnetic field, which also reduces volume than LTS. In this study, the field superposition theory combined with linear programming and nonlinear optimization is introduced in advance to get minimum volume. Considering the different advantages of LTS magnets and HTS magnets, three hybrid MRI magnet configurations are introduced: (1) HTS insert and LTS outsert: (2) Minimum HTS magnet under LTS magnet: (3) Minimum LTS magnet under HTS magnet. In addition, the homogeneity over the central sphere volume and the scope of 5 Gauss fringe field are considered in actively shielding MRI design. Finally, the three different configurations are compared and a 7 T hybrid actively shielding MRI magnet is presented. The designed magnet homogeneity and 5 Gauss fringe field are validated by finite element simulation method, which illustrates the efficiency and the flexibility of the proposed optimal method.