Effect of Strain Relief Loop Position on the RF-Induced Heating of Active Implantable Medical Devices at 1.5-T MRI

This article studies the impact of strain relief loops on RF-induced heating of active implantable medical devices (AIMDs) during magnetic resonance imaging (MRI) scans at 1.5 T. Two commercially available AIMDs, a 40-cm lead length peripheral nerve stimulator (PNS) and a 60-cm lead length spinal cord stimulator (SCS), were utilized. In the in vitro study, lead-tip heating was calculated using the transfer function (TF) method and compared to direct measurement results for strain relief loops at various locations. In the human model analysis, RF-induced heating along six PNS and two SCS trajectories within the Duke, Ella, and FATS models was evaluated for strain relief loops positioned at various locations along the implantation trajectories. From the in vitro study, we can see up to a 48.3% reduction in the overall lead-tip heating. Inappropriate placement may result in doubled temperature rises. Significant temperature rise variation (up to 9°C) is observed with loop position, loop diameter, number of turns, and patient landmark. Differentiation of cumulative summation analysis is necessary to comprehend the strain relief loop's effect on RF-induced heating. The findings suggest that strategically placing the loop can effectively mitigate RF-induced heating for AIMDs exposed to 1.5-T MR environments.