A Fast B 1 + -Driven RF Co-Simulation Optimization Method for RF Coil Arrays

To generate accurate EM simulation models of RF coil arrays, improve coil safety validation procedures, and improve RF power management without sacrificing patient safety.

A fast, customized RF co-simulation formulation was developed for pTx RF coils, enabling the use of experimentally measured $B_1^{+}$ maps to optimize the values of lumped elements, phase shifters, and attenuators in the EM simulation model, and demonstrate in a phantom. The proposed method was tested on an 8-channel pTx knee coil at 7T and a 16-channel pTx head coil at 10.5T. An RF co-simulation optimization method that relies solely on matching the simulated and experimental $S$ -matrices was also implemented as a baseline. 50,000 random RF shims were used to evaluate the $B_1^{+}$ error for both co-simulation optimization methods.

The proposed $B_1^{+}$ -driven co-simulation optimization method generated accurate $B_1^{+}$ maps when compared to experimentally measured $B_1^{+}$ maps. The proposed method reduced the average NRMSE of the EM modeling against the measurements from 48.0% to 30.8% for the 7T 8-channel coil, and from 91.1% to 50.9% for the 10.5T 16-channel coil when compared to conventional methods using 50,000 random RF shims.

The developed $B_1^{+}$ -driven RF co-simulation optimization method in this work can be used to generate a more accurate EM simulation model of custom-built arrays and potentially reduce the need for large safety margins, with improved RF power management.