A lightweight magnetically shielded room with active shielding

A lightweight magnetically shielded room with active shielding

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 developme...

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Bibliographic Details
Published in:Scientific reports Vol. 12; no. 1; pp. 13561 - 13
Main Authors: 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
Format: Journal Article
Language:English
Published: London Nature Publishing Group UK 09-08-2022
Nature Publishing Group
Nature Portfolio
Subjects:
631/378
639/766/25
692/700/1421
692/700/1421/65
Brain
Functional Neuroimaging
Humanities and Social Sciences
Humans
Magnetic Fields
Magnetic Resonance Imaging
Magnetic Resonance Spectroscopy
Magnetoencephalography
Magnetoencephalography - methods
multidisciplinary
Neuroimaging
Science
Science (multidisciplinary)
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Summary: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.
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ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-022-17346-1