Depth-electrode stimulation and concurrent functional MRI in humans: Factors influencing heating with body coil transmission

Hiroyuki Oya; Ralph Adolphs; Matthew A. Howard; J. Michael Tyszka

doi:10.1016/j.nicl.2025.103741

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Depth-electrode stimulation and concurrent functional MRI in humans: Factors influencing heating with body coil transmission

Journal article

Open access

Peer reviewed

Depth-electrode stimulation and concurrent functional MRI in humans: Factors influencing heating with body coil transmission

Hiroyuki Oya, Ralph Adolphs, Matthew A. Howard and J. Michael Tyszka

NeuroImage clinical, Vol.45, 103741

01/25/2025

DOI: 10.1016/j.nicl.2025.103741

PMCID: PMC11821395

PMID: 39889543

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Abstract

•Functional MRI in the presence of electrically long connection leads for implanted depth electrodes presents a variety of risks to the patient, especially from local radiofrequency heating from body coil transmission.•Experiments using typical fMRI sequences at two independent 3 T MRI sites with body coil transmission resulted in only a modest equilibrium temperature rises at electrode contacts, in most cases less than 0.75°.•Both single- and multiband echo planar imaging (EPI) sequences for fMRI have intrinsically low |B1+|rms and correspondingly small local RF electrode heating under the configurations tested.•Local RF electrode heating can exceed 1.5° with high |B1+|rms sequences when connection leads run along the magnet bore surface, but this effect depends strongly on MRI system manufacturer and is easily mitigated by appropriate cable routing. Electrical-stimulation fMRI (es-fMRI) combines direct stimulation of the brain via implanted electrodes with simultaneous rapid functional magnetic resonance imaging of the evoked response. Widely used to map effective functional connectivity in animal studies, its application to the human brain has been limited due to safety concerns. In particular, the method requires reliable prediction and minimization of local tissue heating close to the electrodes, which will vary with imaging parameters and hardware configurations. Electrode leads for such experiments typically remain connected to stimulators outside the magnet room and cannot therefore be treated as electrically short at the radio frequencies employed for 1.5 T and 3 T fMRI. The potential for significant absorption and scattering of radiofrequency energy from excitation pulses during imaging is therefore a major concern. We report a series of temperature measurements conducted in human brain phantoms at two independent imaging centers to characterize factors effecting RF heating of electrically long leads with body coil transmission at 3 Tesla for temporal RMS RF transmit fields (B1+rms) up to 3.5 µT including multiband echo planar imaging and 3D T2w turbo spin echo imaging. Under all conditions tested, with one exception, the temperature rise measured immediately adjacent to electrode contacts in a head-torso phantom with body coil RF transmission was less than 0.75 °C. We provide detailed quantification across a range of configurations and conclude with specific recommendations for cable routing that will help ensure the safety of es-fMRI in humans and provide essential data to institutional review boards.

Electrode

Functional

Heating

Intracranial

MRI

Radiofrequency

Stimulation

Details

Title: Subtitle: Depth-electrode stimulation and concurrent functional MRI in humans: Factors influencing heating with body coil transmission
Creators: Hiroyuki Oya - University of Iowa
Ralph Adolphs - California Institute of Technology
Matthew A. Howard - University of Iowa
J. Michael Tyszka - California Institute of Technology
Resource Type: Journal article
Publication Details: NeuroImage clinical, Vol.45, 103741
DOI: 10.1016/j.nicl.2025.103741
PMID: 39889543
PMCID: PMC11821395
NLM abbreviation: Neuroimage Clin
ISSN: 2213-1582
eISSN: 2213-1582
Publisher: Elsevier Inc
Grant note: NIH/NINDS
The authors are extremely grateful to Dr. Dan Thedens of the Iowa Institute for Biomedical Imaging for porting pulse sequences to the GE Premier system. We thank Vincent Magnotta and Autumn Craig for their help with experimental testing, and Charles Romans and Mike Sneller for help fabricating the skull-torso phantom used at Site 2. This work was funded in part by NIH/NINDS grant U01 NS103780. This work was conducted on an MRI instrument funded by S10OD025025.
Language: English
Date published: 01/25/2025
Academic Unit: Neurology; Iowa Neuroscience Institute; Neurosurgery; Otolaryngology
Record Identifier: 9984781275402771

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