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Multi-channel whole-head OPM-MEG: Helmet design and a comparison with a conventional system

Hill, Ryan M.; Boto, Elena; Rea, Molly; Holmes, Niall; Leggett, James; Coles, Laurence A.; Papastavrou, Manolis; Everton, Sarah; Hunt, Benjamin A.E.; Sims, Dominic; Osborne, James; Shah, Vishal; Bowtell, Richard; Brookes, Matthew J.

Multi-channel whole-head OPM-MEG: Helmet design and a comparison with a conventional system Thumbnail


Authors

Ryan M. Hill

Molly Rea

NIALL HOLMES NIALL.HOLMES@NOTTINGHAM.AC.UK
Mansfield Research Fellow

JAMES LEGGETT JAMES.LEGGETT@NOTTINGHAM.AC.UK
Technical Specialist - Opm Meg

Laurence A. Coles

Manolis Papastavrou

Sarah Everton

Benjamin A.E. Hunt

Dominic Sims

James Osborne

Vishal Shah



Abstract

© 2020 The Authors Magnetoencephalography (MEG) is a powerful technique for functional neuroimaging, offering a non-invasive window on brain electrophysiology. MEG systems have traditionally been based on cryogenic sensors which detect the small extracranial magnetic fields generated by synchronised current in neuronal assemblies, however, such systems have fundamental limitations. In recent years, non-cryogenic quantum-enabled sensors, called optically-pumped magnetometers (OPMs), in combination with novel techniques for accurate background magnetic field control, have promised to lift those restrictions offering an adaptable, motion-robust MEG system, with improved data quality, at reduced cost. However, OPM-MEG remains a nascent technology, and whilst viable systems exist, most employ small numbers of sensors sited above targeted brain regions. Here, building on previous work, we construct a wearable OPM-MEG system with ‘whole-head’ coverage based upon commercially available OPMs, and test its capabilities to measure alpha, beta and gamma oscillations. We design two methods for OPM mounting; a flexible (EEG-like) cap and rigid (additively-manufactured) helmet. Whilst both designs allow for high quality data to be collected, we argue that the rigid helmet offers a more robust option with significant advantages for reconstruction of field data into 3D images of changes in neuronal current. Using repeat measurements in two participants, we show signal detection for our device to be highly robust. Moreover, via application of source-space modelling, we show that, despite having 5 times fewer sensors, our system exhibits comparable performance to an established cryogenic MEG device. While significant challenges still remain, these developments provide further evidence that OPM-MEG is likely to facilitate a step change for functional neuroimaging.

Citation

Hill, R. M., Boto, E., Rea, M., Holmes, N., Leggett, J., Coles, L. A., …Brookes, M. J. (2020). Multi-channel whole-head OPM-MEG: Helmet design and a comparison with a conventional system. NeuroImage, 219, Article 116995. https://doi.org/10.1016/j.neuroimage.2020.116995

Journal Article Type Article
Acceptance Date May 23, 2020
Online Publication Date May 29, 2020
Publication Date Oct 1, 2020
Deposit Date Jun 1, 2020
Publicly Available Date Jun 9, 2020
Journal NeuroImage
Print ISSN 1053-8119
Electronic ISSN 1095-9572
Publisher Elsevier
Peer Reviewed Peer Reviewed
Volume 219
Article Number 116995
DOI https://doi.org/10.1016/j.neuroimage.2020.116995
Keywords Optically pumped magnetometer; OPM; Magnetoencephalography; MEG; beta; gamma
Public URL https://nottingham-repository.worktribe.com/output/4550923
Publisher URL https://www.sciencedirect.com/science/article/pii/S105381192030481X

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