Read My Leads: Subject-Specific RF Hazard Assessment and Mitigation for DBS Implants in MRI

To develop and validate a framework for personalized, implant-specific MRI safety assessments using feedback from commercial deep brain stimulation (DBS) systems. To further use this framework to suppress RF-induced heating with minimum compromise in imaging performance.

Two off-the-shelf DBS implantable pulse generators and a commercial 8-electrode DBS lead were utilized for quantitative safety assessments. In controlled phantom experiments, (i) RF-induced voltages on the DBS lead, and (ii) temperature-dependent admittance/impedance changes in the tissue surrounding the lead's electrodes were quantified. This information was used to suppress implant-related RF heating by calculating implant-friendly imaging modes. Experimental conditions included excitations with different RF transmit coils (8-channel 3 T and 7 T head coils, 2-channel 3 T body coil), over 1000 different exposure scenarios, different implant configurations, and the use of external reference probes ( $E$ -field and temperature) for validation. Imaging performance of the applied implant-friendly mode was demonstrated in vivo on a 3 T scanner.

$E$ -fields and temperature rises around the tip electrodes could be robustly detected directly from the DBS lead. Both signals quantify the momentary patient hazard. Utilizing these measurements-recorded and wirelessly transmitted by the DBS system-tissue heating was reduced up to 99% for the same transmission power with comparable imaging performance to a conventional imaging mode.

All the information needed for full in situ control of implant heating in MRI can be read directly from the DBS device. This approach would improve both patient safety and image quality while simultaneously reducing workload and responsibilities of the clinical personnel.