Evaluation of local B ₁ field as dosimeter of RF heating for implant in MRI

Abstract

Radio frequency (RF) heating is a serious risk for a patient with an elongated implant during MRI scan. The conventional dosimeter of specific absorption rate (SAR) and the recently proposed B 1+rms may not accurately indicate the implant heating. The local B 1 field around the tip of a lead and its relationship with the RF heating were studied by numerical simulations. It was found that regardless of the route of the lead, the angle or position of placement, there was a strong linear correlation between the averaged square of local B 1 field and the rise in temperature. The evaluation range had an effect on the linearity. Generally, the local B 1 field performed better as a dosimeter of RF heating than SAR or B 1+rms at the isocentre.

Subthalamic Nucleus Deep Brain Stimulation Modulates 2 Distinct Neurocircuits

“…The challenge of investigating DBS effects on the human brain using 3T fMRI is the potential risk of brain damage caused by the possible displacement, heating, or radiofrequency‐induced stimulation of the implanted DBS system. To ensure safety, our group recently investigated the displacement force, torque, and vibration of the stimulator during long‐duration 3T MRI scanning 24,25 . Results demonstrated that the hazardous effect in the worst case was 0.17N for displacement force, 8mN·m for torque, and 52.4m/s 2 for vibration 26 .…”

“…To ensure safety, our group recently investigated the displacement force, torque, and vibration of the stimulator during long-duration 3T MRI scanning. 24,25 Results demonstrated that the hazardous effect in the worst case was 0.17N for displacement force, 8mNÁm for torque, and 52.4m/s 2 for vibration. 26 These values were only 46%, 36%, and 8% of the safety thresholds defined by the American Society for Testing and Materials 27,28 and thus met the safety requirements.…”

In-Human Assessment of Radio Frequency Induced Heating for Implants during MRI

“…However, this technique required hardware redesign of IMDs, and may introduce additional artifacts during MRI. Additionally, some studies reported the use of B1 (RF field) mapping methods [37][38][39][40] and the MRI-based determination of the transfer function (TF) of implants 41 , primarily measuring RF-induced currents in the conductive leads. Nevertheless, B1 and TF methods do not directly quantify the IMDs heating and require additional calibration or modelling.…”

Deep brain stimulation of the nucleus basalis of Meynert modulates hippocampal–frontoparietal networks in patients with advanced Alzheimer’s disease

“…A neurostimulator (G106R; Beijing PINS Medical Co., Ltd.) was also connected to the leads (model E202C; Beijing PINS Medical Co., Ltd.). This DBS system is reportedly safe for long-duration 3 T MRI [14][15][16]. Postoperative MRI was performed to confirm the location of the leads and identify signs of cerebral hemorrhage after surgery (Fig.…”