3-Tesla MRI of deep brain stimulation patients: safety assessment of coils and pulse sequences

Abstract

OBJECTIVEPhysicians are more frequently encountering patients who are treated with deep brain stimulation (DBS), yet many MRI centers do not routinely perform MRI in this population. This warrants a safety assessment to improve DBS patients’ accessibility to MRI, thereby improving their care while simultaneously providing a new tool for neuromodulation research.METHODSA phantom simulating a patient with a DBS neuromodulation device (DBS lead model 3387 and IPG Activa PC model 37601) was constructed and used. Temperature changes at the most ventral DBS electrode contacts, implantable pulse generator (IPG) voltages, specific absorption rate (SAR), and B1+rms were recorded during 3-T MRI scanning. Safety data were acquired with a transmit body multi-array receive and quadrature transmit-receive head coil during various pulse sequences, using numerous DBS configurations from “the worst” to “the most common.”In addition, 3-T MRI scanning (T1 and fMRI) was performed on 41 patients with fully internalized and active DBS using a quadrature transmit-receive head coil. MR images, neurological examination findings, and stability of the IPG impedances were assessed.RESULTSIn the phantom study, temperature rises at the DBS electrodes were less than 2°C for both coils during 3D SPGR, EPI, DTI, and SWI. Sequences with intense radiofrequency pulses such as T2-weighted sequences may cause higher heating (due to their higher SAR). The IPG did not power off and kept a constant firing rate, and its average voltage output was unchanged. The 41 DBS patients underwent 3-T MRI with no adverse event.CONCLUSIONSUnder the experimental conditions used in this study, 3-T MRI scanning of DBS patients with selected pulse sequences appears to be safe. Generally, T2-weighted sequences (using routine protocols) should be avoided in DBS patients. Complementary 3-T MRI phantom safety data suggest that imaging conditions that are less restrictive than those used in the patients in this study, such as using transmit body multi-array receive coils, may also be safe. Given the interplay between the implanted DBS neuromodulation device and the MRI system, these findings are specific to the experimental conditions in this study.

Functional MRI Safety and Artifacts during Deep Brain Stimulation: Experience in 102 Patients

“…In a previous study (15), we reported on 41 participants included in our current study. The current study expands on that study by using body transmit-receive coils and includes analyses characterizing DBS metallic artifacts seen on images from functional MRI.…”

“…The DBS models used are summarized in Figure 2. Participants undergoing 3-T MRI were also required to have DBS hardware geometry similar to previous phantoms (15,19,23), with redundant extension wire coiled into an extension loop (approximately 2 cm in diameter) under the scalp and the remainder of excess wire coiled behind a subclavicular IPG (Fig 3). Participants were excluded if they were unable to provide informed consent (eg, they had cognitive, psychologic, or communication impairments).…”

“…To date, investigators have used phantom models replicating the configuration of DBS neuromodulation devices in individuals to explore the MRI safety of DBS hardware outside of vendor guidelines (14)(15)(16)(17)(18)(19). The main safety issue addressed with phantom experiments is heating of the DBS neuromodulation system (20).…”

“…Experiments in phantoms have yielded inconsistent results with regard to safe MRI of DBS; this is due in part to the heterogeneous and continually evolving DBS and MRI hardware (21,22). Notably, recent phantom studies have demonstrated an acceptable temperature rise at the electrodes when using 3-T MRI and a body transmit coil (15,19,23).…”

Comparison between 1.5- and 3-T Magnetic Resonance Acquisitions for Direct Targeting Stereotactic Procedures for Deep Brain Stimulation: A Phantom Study

“…Advantages and pitfalls associated with the use of 3-T scanners have now been well described [10,11]. Boutet et al [12] demonstrated the safety of coils and pulse sequences of 3-T MRI of DBS patients. Voormolen et al [13] found no visible intracranial distortion in magnetization-prepared T1-weighted 7-T MRI cranial images but considerable extracranial shifts for image-guided cranial neurosurgery.…”