Journal Article

RF-induced heating in tissue near bilateral DBS implants during MRI at 1.5 T and 3T: The role of surgical lead management

Downs, Sean, Martin, Alastair, Pilitsis, Julie, Kirsch, John, Bonmassar, Giorgio, Keil, Boris, Wald, Lawrence L., Iacono, Maria-Ida, Angelone, Leonardo M., Golestanirad, Laleh, Elahi, Behzad

2019

Overview

Access to MRI is limited for patients with deep brain stimulation (DBS) implants due to safety hazards, including radiofrequency (RF) heating of tissue surrounding the leads. Computational models provide an exquisite tool to explore the multi-variate problem of RF heating and help better understand the interaction of electromagnetic fields and biological tissues. This paper presents a computational approach to assess RF-induced heating, in terms of specific absorption rate (SAR) in the tissue, around the tip of bilateral DBS leads during MRI at 64MHz/1.5 T and 127 MHz/3T. Patient-specific realistic lead models were constructed from post-operative CT images of nine patients operated for sub-thalamic nucleus DBS. Finite element method was applied to calculate the SAR at the tip of left and right DBS contact electrodes. Both transmit head coils and transmit body coils were analyzed. We found a substantial difference between the SAR and temperature rise at the tip of right and left DBS leads, with the lead contralateral to the implanted pulse generator (IPG) exhibiting up to 7 times higher SAR in simulations, and up to 10 times higher temperature rise during measurements. The orientation of incident electric field with respect to lead trajectories was explored and a metric to predict local SAR amplification was introduced. Modification of the lead trajectory was shown to substantially reduce the heating in phantom experiments using both conductive wires and commercially available DBS leads. Finally, the surgical feasibility of implementing the modified trajectories was demonstrated in a patient operated for bilateral DBS. •Access to MRI is limited for patients with DBS implants due to safety hazards, including radiofrequency heating of tissue surrounding the leads.•Computational models provide an exquisite tool to explore the multi-variate problem of RF implant heating.•We used a computational approach to assess RF heating around tips of bilateral DBS leads during MRI at 1.5T and 3T using realistic DBS lead models.•A substantial difference was found between the SAR and temperature rise at the tip of right and left DBS leads.•Modification of DBS lead trajectory reduced heating in phantom experiments using both conductive wires and commercially available DBS leads.

• Publisher: Elsevier Inc,Elsevier Limited
• Subject: Computational modeling and simulations / Computational neuroscience / Computer Simulation / Deep brain stimulation / Deep brain stimulation (DBS) / Deep Brain Stimulation - instrumentation / Electrodes, Implanted / Electromagnetic Fields / Experiments / Finite element method / Finite element method (FEM) / Hot Temperature / Humans / Magnetic resonance imaging / Magnetic resonance imaging (MRI) / Magnetic Resonance Imaging - adverse effects / Magnetic Resonance Imaging - methods / Medical implants / Models, Theoretical / MRI safety / Neuromodulation / Neurostimulation / NMR / Nuclear magnetic resonance / Patients / Phantoms, Imaging / Radio Waves / Simulation / Specific absorption rate (SAR) / Thalamus / Transplants & implants