Combining the advantages of FDTD and FEM for MRI RF safety evaluation using the Huygens method

Motivation: MRI RF safety evaluation requires simulations of many coils and body models, which is typically done using FDTD or FEM. These have complementary weaknesses, therefore we propose to combine them. Goal(s): We propose a simulation process that combines FEM with FDTD via the Huygens’ principle. Approach: We first compute the incident electric field created by the coil alone using FEM. Second, we compute field perturbations created by the body model using an FDTD Huygens’ implementation. Results: The proposed method agrees well with the all-FDTD calculation at 64 MHz, but allows more efficient and flexible modelling of RF coils. Impact: We propose a robust and flexible simulation method combining the strengths of FEM and FDTD via the Huygens principle that expedites coil and implant (ISO/TS10974 Tier 3) RF safety evaluations.