A Resistive Tapered Cylindrical Conductor Can Substantially Reduce RF Heating of Implanted Leads During MRI: A...

Active implanted electronic devices (AIMDs) are increasingly common and are often indicated to provide therapeutic stimulation to patients in cases such as pacemakers and deep brain stimulators. Such devices typically require leads of significant length to deliver stimulation. The use of long leads in combination with an implantable pulse generator often means that there is a significant risk of radiofrequency energy coupling with the leads when patients receive MRI scans. Previous studies have investigated the use of a multi-segment wires with sharp conductivity changes to mitigate this RF coupling. However, past work in this area has evaluated stripline and straight cylindrical geometries. Clinical lead designs often use helical wrapping for internal conductors for improved fatigue resistance. In this study we assessed the applicability of the multi-segment lead design with a helical structure at 1.5 T to better assess the potential heating reduction with a more clinically relevant geometry. A maximum SAR reduction of roughly 7-fold was achieved, and decreasing the helical pitch yielded shorter optimum lengths for the tissue-exposed wire segment.