RF Heating Dependence of Head Model Positioning Using 4-Channel Parallel Transmission MRI and a Deep Brain Stimulation Construct

Abstract

Parallel radiofrequency transmission (pTx) continues to demonstrate promise in addressing magnetic resonance imaging (MRI) challenges at higher magnetic-field strengths, particularly regarding the safety of patients with implanted deep brain stimulation (DBS) devices. Radiofrequency (RF) shimming optimization methods have shown the potential of pTx to minimize DBS implant safety concerns relating to induced RF heating at 3T. This letter continues the assessment of 4-channel pTx technology and its associated “safe mode” for the DBS application. Safe mode sensitivity to patient setup mispositioning and movement is important and was studied in proof-of-concept. Phantom mispositioning can impact the electromagnetic near-field distribution and potentially affect the RF heating effects along an implanted DBS device. However, thermal simulations studying DBS patient head movements were performed and indicated minimal safety risks. These results were further validated by an MRI phantom mispositioning experiment encompassing the head motion studied in simulation. Temperature increases remained below +1°C for all tested scenarios in simulation and experiment. However, a severe pitch rotation in the experiment led to a +0.8°C increase, indicating that significant patient movement may still shift implanted DBS leads into higher risk zones. In conclusion, this letter further supports the potential of 4-channel pTx to address DBS patient safety.