A Novel Lead Construct to Reduce MRI-Induced RF Heating: Construction, In Vitro Validation, and In Vivo Predictions.

Area of Science:

• Biomedical Engineering
• Medical Imaging Physics

Background:

• Radiofrequency (RF) heating of conductive leads in active implantable medical devices (AIMDs) poses a significant safety risk during Magnetic Resonance Imaging (MRI).
• Existing AIMDs often have limitations for MRI compatibility due to potential lead heating, restricting diagnostic imaging options for patients.

Purpose of the Study:

• To develop and validate novel resistively tapered cylindrical (RTC) leads designed to intrinsically suppress RF heating during MRI.
• To assess the efficacy of RTC leads in reducing RF-induced temperatures compared to conventional leads.

Main Methods:

• Fabrication of two-segment RTC wire prototypes using thin-film physical vapor deposition to introduce axial conductivity discontinuities.
• In vitro validation of lead transfer functions through heating experiments at 1.5 T and comparison with a uniform conductivity control wire.
• Electromagnetic simulations incorporating calibrated transfer functions for 210 realistic deep brain stimulation (DBS) trajectories in a full-body model to predict in vivo heating.

Main Results:

• RTC wires demonstrated a greater than 60% reduction in peak RF-induced temperature rise at the tip compared to control wires in vitro.
• In vivo predictions showed a greater than 20% reduction in mean tip heating and a 20-fold lower peak heating compared to a commercial DBS lead.
• The developed RTC leads significantly attenuated MRI-induced RF heating without substantial geometric modifications.

Conclusions:

• Axial conductivity tapering is an effective strategy for mitigating MRI-induced RF heating in implantable leads.
• Conductivity-tailored leads offer a viable pathway toward inherently MRI-compatible AIMDs, potentially increasing access to advanced diagnostic imaging for a broader patient population.