Comparison of Different Assessment Quantities to Evaluate Lead Electromagnetic Model for Radio Frequency Energy-Induced Heating

Abstract

To prevent tissue damage near an active implantable medical device (AIMD), the radio frequency energy-induced heating must be estimated for all possible clinical scenarios in patients undergoing magnetic resonance imaging. Four quantities, namely 1) the net dissipated power around an electrode of an AIMD, 2) the net temperature increase, 3) the current flowing from the lead to the electrode, and 4) the net specific absorption rate (SAR) increase were numerically compared for a set of leads to evaluate the analytical lead electromagnetic model (LEM) with respect to radio frequency energy-induced heating. The lead set included 32 generic single electrode leads with straight and helical wires. The LEMs were obtained and validated with 3D electromagnetic and thermal co-simulations at 128 MHz. A shift of the position of temperature or SAR sensor from the electrode tip to the electrode pedestal resulted in a decrease of the linear regression coefficient of determination for the LEM calibration factors. Behavior of different assessment quantities in terms of sensitivity of sensor location significantly varied between leads with the helical and straight wires. In conclusion, utilization of result analysis made for generic leads with straight wire can be significantly misleading for the prediction of results for leads with helical wires.