A Hybrid FDTD-FEM Simulation Approach For Safety Assessment of Geometrically Complex Birdcage Coils.

Motivation: RF safety assessment requires accurate simulation results. FEM simulations offer superior performance for delicate structures while FDTD simulations are more efficient for realistic body models. Goal(s): Improve the accuracy of FDTD simulations for four-layered body coil models using a simplified, three layered, model combined with network co-simulation. Approach: In Sim4Life, a body coil is simulated using lumped element capacitors instead of layered capacitor structures. Capacitor values are optimized by network co-simulation to minimize differences in the resulting E-field distribution and that of HFSS. Results: Improved E-field and B1+ field distributions are observed in common phantoms for whole-body SAR and implant local SAR assessment. Impact: The proposed method can accurately simulate complex birdcage body coils with layered capacitor structures while also being able to include realistic body models. As such, the method combines the features of FDTD and FEM simulations.