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A Novel Lead Construct to Reduce MRI-Induced RF Heating: Construction, In Vitro Validation, and In Vivo Predictions
Objective:
Magnetic resonance imaging (MRI) of patients with active implantable medical devices is restricted by radiofrequency (RF) heating of conductive leads. Our goal was to develop and validate resistively tapered cylindrical (RTC) leads that intrinsically suppress RF heating.
Methods:
Two-segment RTC wire prototypes (RTC1, RTC2) were fabricated by thin-film physical vapor deposition to create axial conductivity discontinuities. The transfer functions for both were measured and validated with in vitro heating experiments at 1.5 T along 12 trajectories and benchmarked against a uniform conductivity control wire. Calibrated transfer functions were combined with electromagnetic simulations of 210 clinically realistic deep brain stimulation (DBS) trajectories in an anatomically detailed full-body model to predict in vivo heating, with a commercial DBS lead included for comparison.
Results:
Gel phantom experiments showed the RTC wires cut peak RF-induced temperature rise at the tip by $>$60% versus the control wire in vitro, lowering the mean heating from 3.67 to 1.43. The in vivo predictions using the transfer function methodology showed a $>$20% reduction in the mean tip heating vs. the uniform conductivity wire ($p< 0.001$) and a 20-fold lower peak heating compared to a commercial DBS lead under identical exposure conditions.
Conclusion:
Axial conductivity tapering markedly attenuates MRI-induced RF heating without requiring significant changes to lead geometry.
Significance:
Conductivity-tailored leads provide a practical path toward inherently MRI-compatible AIMDs, potentially expanding diagnostic imaging access for millions of patients.
