Simulating the Magnetic Field of a Nonlinear and Time-Varying Arbitrary-Nucleus Coil

Motivation: An untuned, non-resonant coil called the ADAPT Coil has recently been developed to excite any nucleus in high field, human-scale MRI. However, the coil’s nonlinear and time-varying characteristics render conventional simulation methods insufficient. Goal(s): To develop an accurate simulation method for nonlinear and time-varying coils. Approach: A finite-difference time-domain solver and a harmonic balance simulator were combined to simulate the linear components and the nonlinear and time-varying components, respectively. Results: Nonlinear and time-varying coil operation was simulated and the resulting magnetic fields for five harmonics were visualized. The fundamental frequency magnetic field resembles that of an ideal current loop. Impact: If validated for use with humans, the ADAPT Coil would significantly reduce barriers to clinical translation of X-nuclei research. The simulation method presented here represents a major step towards validation of the ADAPT Coil or any other nonlinear coil.