RF-induced Heating for Partially-In and Partially-Out Bipolar Parallel Medical Electrodes.

RF-induced heating is evaluated for unipolar and bipolar Partially-In and Partially-Out (PIPO) medical electrodes at 1.5T MRI. Numerical simulations were performed by modeling simplified unipolar and bipolar electrodes to understand the RF heating mechanism. Then, experimental studies inside the ASTM phantom were performed using a 60 cm long commercial unipolar and bipolar PIPO cardiac pacing electrodes. In addition, transfer function models were developed, scaled, and validated for 60 cm pacing electrodes, and in-vivo heating was estimated for 30-minute RF exposure using the standard medium. The results show that the RF heating for the bipolar PIPO medical electrode is lower than the unipolar PIPO electrode due to coupling between the parallel leads. However, this study uses limited clinical trajectories for the external pacing application; heating could differ for other possible trajectories, devices, or applications.