Comparative study of radiofrequency heating in deep brain stimulation devices during MRI at 1.5 T and 0.55 T: Challenging the assumption of safety at low field strengths.

Abstract

<h4>Purpose</h4>Low-field MRI has been assumed to be implant-friendly based on limited studies. However, radiofrequency (RF)-induced heating due to an implant is a complex resonance phenomenon, highly dependent on the implant's configurations and applied RF frequencies. This study aims to evaluate the RF heating of deep brain stimulation (DBS) implants during MRI at low field strengths compared with higher-field 1.5T MRI.<h4>Methods</h4>A commercial DBS implant was used in full system as well as lead-only configurations to evaluate and compare RF heating during MRI at 0.55 T and 1.5 T. The transfer function of the device was measured and validated at each of the frequencies, which was then used for prediction of RF heating with realistic DBS configurations at head, chest, and abdomen imaging landmarks.<h4>Results</h4>For the lead-only case, the RF heating due to the DBS was substantially smaller during imaging at 0.55 T compared with that at 1.5 T. However, for the full DBS system (longer implant), the RF heating at 0.55 T was comparable to, and for some cases even higher than, that at 1.5 T, reaching a level that poses risk of tissue damage in patients.<h4>Conclusions</h4>Although RF heating generally tends to be lower at low-field MRI, the case with longer implanted leads demands extra caution, due to the higher possibility of matching resonant condition at low-field-strength frequencies. Thus, specific risk evaluation for each implant and configuration is required rather than assuming that lower field strength imaging is safer.