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

Laleh Golestanirad, John Kirsch, Giorgio Bonmassar, Sean Downs, Behzad Elahi, Alastair Martin, Maria-Ida Iacono, Leonardo M. Angelone, Boris Keil, Lawrence L. Wald, Julie Pilitsis - Department of Radiology, Feinberg School of Medicine, Northwestern University, Chicago, USA; Department of Biomedical Engineering, McCormick School of Engineering, Northwestern University, Evanston, USA; A. A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Boston, USA; Department of Neurology, Mayo Clinic, Rochester, USA; Department of Radiology and Biomedical Imaging, University of California, San Francisco, USA; Division of Biomedical Physics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, SilverSpring, USA; Department of Life Science Engineering, Institute of Medical Physics and Radiation Protection, Giessen, Germany; Department of Neurosurgery, Albany Medical Center, Albany, USA

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.

How Amira-Avizo Software is used

Amira 5.3 was used for image segmentation and construction of the preliminary 3D surface of the leads. First, a thresholding mask was applied to select the hyper dense DBS lead from CT images using Amira’s segmentation module. Threshold values were selected manually on a case-by-case basis such that the resulting mask covered the center of the artifact but not the surrounding tissue such as bone. Labels were smoothed with a Gaussian filter (3×3 pixel size) and the resulting mask was used to generate preliminary 3D surfaces of the lead trajectories.