Prevalence of Complications in Intraoperative Magnetic Resonance Imaging Combined with Neurophysiologic Monitoring.
OBJECTIVE
High-field intraoperative magnetic resonance imaging (ioMRI) is becoming increasingly available in neurosurgery centers, where it has to be combined with intraoperative neurophysiologic monitoring (IONM). IONM needle electrodes remain on the patient during ioMRI and may cause image distortions and burns. We tested magnetic resonance (MR) -heating experimentally and investigated the prevalence of complications.


METHODS
We studied electrodes that are certified for IONM, but not "MR conditional." They consist of copper cables (length, 1.5 m) and needles made of either stainless steel (ferromagnetic) or paramagnetic platinum/iridium alloy. We simulated an ioMRI session with gel and measured the temperature increase with optical fibers. We measured the force that an electrode experiences in the magnetic field. Between 2013 and 2016, we prospectively documented subcutaneous needle electrodes that remained in the patient during intraoperative 3 Tesla ioMRI scans.


RESULTS
The in vitro testing of the electrodes produced a maximum heating (ΔT = 3.9°C) and force of 0.026 N. We placed 1237 subcutaneous needles in 57 surgical procedures with combined IONM and ioMRI, where needles remained in place during ioMRI. One patient suffered a skin burn on the shoulder. All other electrodes had no side effects.


CONCLUSIONS
We have corroborated the history of safe use for electrodes with 1.5 m cable in a 3T MRI scanner and demonstrated their use. Nevertheless, heating cannot be excluded, as it depends on location and cable placement. When leaving electrodes in place during ioMRI, risks and benefits have to be carefully evaluated for each patient.
Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; University of Zurich, Zurich, Switzerland; Zurich Neuroscience Center, University and ETHZ, Zurich, Switzerland. Electronic address: johannes.sarnthein@usz.ch.
Johannes
J
Sarnthein
Institute for Biomedical Engineering, University and ETHZ, Zurich, Switzerland; University of Zurich, Zurich, Switzerland.
Roger
R
Lüchinger
Department of Neuroradiology, University Hospital Zurich, Zurich, Switzerland; University of Zurich, Zurich, Switzerland.
Marco
M
Piccirelli
Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; University of Zurich, Zurich, Switzerland.
Luca
L
Regli
Department of Neurosurgery, University Hospital Zurich, Zurich, Switzerland; University of Zurich, Zurich, Switzerland.
Oliver
O
Bozinov
D000293:Adolescent; D000328:Adult; D000368:Aged; D002058:Burns, Electric / Q000209:etiology* / Q000517:prevention & control; D000075202:Contraindications; D004566:Electrodes / Q000009:adverse effects*; D005260:Female; D006801:Humans; D053783:Magnetic Resonance Imaging, Interventional / Q000295:instrumentation; D008297:Male; D008875:Middle Aged; D064926:Neurophysiological Monitoring / Q000295:instrumentation*; D019635:Neurosurgical Procedures / Q000009:adverse effects* / Q000295:instrumentation; D019047:Phantoms, Imaging; D015995:Prevalence; D012307:Risk Factors; D025321:Surgery, Computer-Assisted / Q000009:adverse effects* / Q000295:instrumentation; D055815:Young Adult
Diamagnetic metal; Electrode cable length; Ferromagnetic metal; Intraoperative MRI; Intraoperative neurophysiologic monitoring; Magnetic force; Paramagnetic metal; RF heating