Specific absorption rate in a standard phantom containing a Deep Brain Stimulation lead at 3 Tesla MRI

Finite elements methods (FEM) simulations are presented showing the specific absorption rate (SAR) distribution in the case of a Deep Brain Stimulation (DBS) lead inside a standard phantom exposed to 128 MHz / 3 Tesla magnetic resonance imaging (MRI). The electromagnetic model is proposed as a tool to study the safety of patients with an implanted DBS lead undergoing clinical 3T MRI systems. The simulations were based on an electromagnetic and circuit co-simulation methodology and allowed for fine tuning of the MRI radiofrequency transmit body coil. Results show that the presence of the lead did not influence the behavior of the coil, namely the S-parameters at the coil feed were largely unaffected by the presence of a lead. Conversely, significant changes of electric and magnetic field, as well as local SAR were observed due to the characteristic antenna effect. The lead path strongly affected the level of SAR at the distal tip of the lead, with a 10x fold difference between the two configurations evaluated.