Simulation of the dB/dt-over-electric field cardiac magnetostimulation safety ratio in 75 body models and 18 gradient systems

Motivation: IEC 60601-2-33 uses simple electromagnetic calculations in a homogeneous ellipsoid to derive the ratio between cardiac stimulation E-field and dB/dt for setting actionable scanner limits. Goal(s): Re-compute the dB/dt-over-E-field ratio using simulations in multiple realistic body models and body gradient coils (GC). Approach: We performed two independent electromagnetic simulation studies of 13 GCs in 56 body models (study #1) and 5 GCs in 19 body models (study #2). Results: The dB/dt-over-E99 ratio (E99 is 99th percentile of E-fields in myocardium) is between 12 (worst-case) and 16 (T/s)*(V/m)-1 (1st percentile), suggesting that some increase beyond the current value of 10 (T/s)*(V/m)-1 may be justified. Impact: Our simulations of the IEC 60601-2-33 cardiac magnetostimulation dB/dt-over-E-field ratio indicate values between 12 and 16 (T/s)*(V/m)-1, which is greater than the current value of 10 (T/s)*(V/m)-1. Increasing this ratio would allow for more liberal use of modern gradient performance.