RF heating of deep brain stimulation implants in open-bore vertical MRI systems: A simulation study with realistic device configurations

Abstract

Purpose: Patients with deep brain stimulation (DBS) implants benefit highly from MRI, however, access to MRI is restricted for these patients because of safety hazards associated with RF heating of the implant. To date, all MRI studies on RF heating of medical implants have been performed in horizontal closed-bore systems. Vertical MRI scanners have a fundamentally different distribution of electric and magnetic fields and are now available at 1.2T, capable of high-resolution structural and functional MRI. This work presents the first simulation study of RF heating of DBS implants in high-field vertical scanners.

Methods: We performed finite element electromagnetic simulations to calculate specific absorption rate (SAR) at tips of DBS leads during MRI in a commercially available 1.2T vertical coil compared to a 1.5T horizontal scanner. Both isolated leads and fully implanted systems were included.

Results: We found 10- to 30-fold reduction in SAR implication at tips of isolated DBS leads, and up to 19-fold SAR reduction at tips of leads in fully implanted systems in vertical coils compared to horizontal birdcage coils.

Conclusions: If confirmed in larger patient cohorts and verified experimentally, this result can open the door to plethora of structural and functional MRI applications to guide, interpret, and advance DBS therapy.

Keywords: MR-guided neurosurgery; MRI safety; RF heating; deep brain stimulation; finite element method (FEM); interventional MRI; medical implants; open-bore MRI; vertical MRI.