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A lightweight magnetically shielded room with active shielding

Holmes, Niall; Rea, Molly; Chalmers, James; Leggett, James; Edwards, Lucy J.; Nell, Paul; Pink, Stephen; Patel, Prashant; Wood, Jack; Murby, Nick; Woolger, David; Dawson, Eliot; Mariani, Christopher; Tierney, Tim M.; Mellor, Stephanie; O’Neill, George C.; Boto, Elena; Hill, Ryan M.; Shah, Vishal; Osborne, James; Pardington, Rosemarie; Fierlinger, Peter; Barnes, Gareth R.; Glover, Paul; Brookes, Matthew J.; Bowtell, Richard

Authors

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

Molly Rea

James Chalmers

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

Lucy J. Edwards

Paul Nell

Stephen Pink

Prashant Patel

Jack Wood

Nick Murby

David Woolger

Eliot Dawson

Christopher Mariani

Tim M. Tierney

Stephanie Mellor

George C. O’Neill

Ryan M. Hill

Vishal Shah

James Osborne

Rosemarie Pardington

Peter Fierlinger

Gareth R. Barnes

PAUL GLOVER paul.glover@nottingham.ac.uk
Associate Professor



Abstract

Magnetically shielded rooms (MSRs) use multiple layers of materials such as MuMetal to screen external magnetic fields that would otherwise interfere with high precision magnetic field measurements such as magnetoencephalography (MEG). Optically pumped magnetometers (OPMs) have enabled the development of wearable MEG systems which have the potential to provide a motion tolerant functional brain imaging system with high spatiotemporal resolution. Despite significant promise, OPMs impose stringent magnetic shielding requirements, operating around a zero magnetic field resonance within a dynamic range of ± 5 nT. MSRs developed for OPM-MEG must therefore effectively shield external sources and provide a low remnant magnetic field inside the enclosure. Existing MSRs optimised for OPM-MEG are expensive, heavy, and difficult to site. Electromagnetic coils are used to further cancel the remnant field inside the MSR enabling participant movements during OPM-MEG, but present coil systems are challenging to engineer and occupy space in the MSR limiting participant movements and negatively impacting patient experience. Here we present a lightweight MSR design (30% reduction in weight and 40–60% reduction in external dimensions compared to a standard OPM-optimised MSR) which takes significant steps towards addressing these barriers. We also designed a ‘window coil’ active shielding system, featuring a series of simple rectangular coils placed directly onto the walls of the MSR. By mapping the remnant magnetic field inside the MSR, and the magnetic field produced by the coils, we can identify optimal coil currents and cancel the remnant magnetic field over the central cubic metre to just |B|= 670 ± 160 pT. These advances reduce the cost, installation time and siting restrictions of MSRs which will be essential for the widespread deployment of OPM-MEG.

Citation

Holmes, N., Rea, M., Chalmers, J., Leggett, J., Edwards, L. J., Nell, P., …Bowtell, R. (2022). A lightweight magnetically shielded room with active shielding. Scientific Reports, 12, Article 13561. https://doi.org/10.1038/s41598-022-17346-1

Journal Article Type Article
Acceptance Date Jul 25, 2022
Online Publication Date Aug 9, 2022
Publication Date Aug 9, 2022
Deposit Date Oct 12, 2022
Publicly Available Date Mar 28, 2024
Journal Scientific Reports
Electronic ISSN 2045-2322
Publisher Springer Science and Business Media LLC
Peer Reviewed Peer Reviewed
Volume 12
Article Number 13561
DOI https://doi.org/10.1038/s41598-022-17346-1
Keywords Multidisciplinary
Public URL https://nottingham-repository.worktribe.com/output/10071782
Publisher URL https://www.nature.com/articles/s41598-022-17346-1

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