Compatibility of Intraoperative 3T MR Imaging and Intraoperative Neurophysiological Monitoring

Aims: During resection of brain tumors, intraoperative magnetic resonance imaging (ioMRI) and intraoperative neurophysiological monitoring (IONM) help the surgical team to determine tumor margins and prevent new neurological deficits. We here study the use of IONM-needles that remain attached to the patient during 3T ioMRI. We evaluate the safety of the needles (movement, heating) and image distortions.

Methods: We first studied image distortions in test measurements with a phantom for three different types of needles: 1) stainless steel corkscrew needle; 2) stainless steel twisted-pair straight needle 15 mm; 3) Platinum/Iridium (Pt/Ir) needle straight needle 15 mm (low magnetic susceptibility). The sequence was MPRAGE (magnetization prepared rapid gradient echo) on the 3T Siemens Skyra for high-resolution T1-weighted images. We then used needle types 2) and 3) in 13 patients, where IONM and 3T MRI was performed.

Results: Phantom measurements showed no relevant image distortion for straight Pt/Ir needles. Patient ioMRI showed no relevant image distortion for straight needles made either of stainless steel or Pt/Ir. There was no movement of straight needles on the patient in ioMRI. There was no skin irritation in the face due to possible heating of straight needles in the ioMRI.

Conclusion: IONM is compatible with 3T ioMRI, if Pt/Ir needles are placed on the scalp. In muscles of the face or limbs, stainless steel EMG needles can be used to record muscle responses.