The effect of device configuration and patient’s body composition on image artifact and RF heating of deep brain stimulation devices during MRI at 1.5T and 3T

Abstract

BACKGROUNDPatients with deep brain stimulation (DBS) implants have limited access to MRI due to safety concerns associated with RF-induced heating. Currently, MRI in these patients is allowed only in 1.5T horizontal scanners and with pulse sequences with reduced power.Nevertheless, off-label use of MRI at 3T is increasingly reported based on limited safety assessments. Here we present results of systematic RF heating measurements for two commercially available DBS systems during MRI at 1.5T and 3T. from 0.10℃ to 7.39℃ at 3T. The presence of subcutaneous fat substantially altered RF heating at electrode tips (-3.06℃ < ∆ < 19.05℃). Introducing concentric loops in the extracranial portion of the lead at the surgical burr hole reduced RF heating by up to 89% at 1.5T and up to 98% at 3T compared to worst case heating scenarios. DATA CONCLUSIONDevice configuration and patient body composition significantly altered the RF heating of DBS leads during MRI at 1.5T and 3T. Interestingly, certain lead trajectories consistently reduced RF heating and image artifact over different imaging landmarks, RF frequencies, and phantom compositions. Such trajectories could be implemented in patients with minimal disruption to the surgical workflow.

Vertical open‐bore MRI scanners generate significantly less radiofrequency heating around implanted leads: A study of deep brain stimulation implants in 1.2T OASIS scanners versus 1.5T horizontal systems

“…Pioneering work has been done to advance MRI field‐shaping methods, techniques that manipulate the electric field of MRI transmit coil to eliminate its interaction with individual patient′s implants 2,9,26,47‐52 . Another alternative approach is surgical device management, where trajectories of implanted leads are surgically modified (based on computer simulations) such that their coupling with MRI electric fields is minimized 8,10,29 . Finally, there has been a spate of patents proposing novel implant structures 53‐57 and materials 11,58 to reduce induced RF currents, and by proxy, RF heating.…”

“…Finally, trajectory IV had no loop on the skull with all excess length of the lead + extension looped around the IPG. This trajectory has been shown to generate maximum RF heating at both 1.5T and 3T horizontal scanners 29 …”

“…Trajectory I consisted of two concentric loops at the surgical burr hole, with the rest of wire/lead routed medio‐laterally toward the neck and the excess length of wire/extension looped around the IPG as recommended in the manufacturer's clinician manual. This configuration has been shown to minimize RF heating of fully implanted DBS devices at 3 T, 29 and is implemented as the standard of care surgical approach by some groups 34 . Trajectory II consisted of two concentric loops moved farther from the surgical burr hole along the coronal suture, which is a common lead arrangement observed on post‐operative CT images.…”

“…RF heating of a conductive implant depends on the distribution of MRI electric fields inside the body and around the implant, which varies by changing the position of the body inside the RF coil 21,28,29 . To investigate the effect of imaging landmark, we performed simulations with the body model positioned either with the head or chest at the coil's iso‐center, corresponding to neuroimaging and cardiac imaging, respectively (Figure 4).…”

“…Trajectory III consisted of two loops above the temporal bone, with the rest of extension/wire routed similar to previous two cases. This lead configuration is shown to reduce RF heating of fully implanted DBS devices at 1.5T 29 and is implemented by some groups to reduce the susceptibility artifact above the motor cortex that contaminates fMRI signal 35 . Finally, trajectory IV had no loop on the skull with all excess length of the lead + extension looped around the IPG.…”