A Novel, Robust and Portable Platform for MEG using OPMs
Poster No:
2130
Submission Type:
Late-Breaking Abstract Submission
Authors:
Holly Schofield1,2, Ryan Hill1,2, Odile Feys3,4, Niall Holmes1,2, James Osborne5, Cody Doyle5, David Bobela5, Pierre Corvilain3, Vincent Wens3,6, Lukas Rier1,2, Richard Bowtell1,2, Maxime Ferez3, Karen Mullinger1,7, Sebastian Coleman1, Natalie Rhodes1, Molly Rea2, Zoe Tanner1,2, Elena Boto2,1, Xavier De Tiege3,6, Vishal Shah5, Matthew Brookes1,2
Institutions:
1Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, Nottingham, United Kingdom, 2Cerca Magnetics Limited, Nottingham, United Kingdom, 3Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag, Brussels, Belgium, 4Department of Neurology, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles, Brussels, Belgium, 5QuSpin Inc., Louisville, CO, 6Department of Translational Neuroimaging, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles, Brussels, Belgium, 7Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, United Kingdom
First Author:
Holly Schofield
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Co-Author(s):
Ryan Hill
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Odile Feys
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Neurology, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Neurology, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Niall Holmes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Pierre Corvilain
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag
Brussels, Belgium
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag
Brussels, Belgium
Vincent Wens
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Translational Neuroimaging, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Translational Neuroimaging, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Lukas Rier
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Richard Bowtell
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Maxime Ferez
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag
Brussels, Belgium
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag
Brussels, Belgium
Karen Mullinger
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Centre for Human Brain Health, School of Psychology, University of Birmingham
Nottingham, United Kingdom|Birmingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Centre for Human Brain Health, School of Psychology, University of Birmingham
Nottingham, United Kingdom|Birmingham, United Kingdom
Sebastian Coleman
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom
Natalie Rhodes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom
Zoe Tanner
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Elena Boto
Cerca Magnetics Limited|Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom|Nottingham, United Kingdom
Cerca Magnetics Limited|Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham
Nottingham, United Kingdom|Nottingham, United Kingdom
Xavier De Tiege
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Translational Neuroimaging, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Université libre de Bruxelles, ULB Neuroscience Institute, Laboratoire de neuroanatomie et neuroimag|Department of Translational Neuroimaging, Hôpital Erasme, Hôpital Universitaire de Bruxelles, Université libre de Bruxelles
Brussels, Belgium|Brussels, Belgium
Matthew Brookes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham|Cerca Magnetics Limited
Nottingham, United Kingdom|Nottingham, United Kingdom
Introduction:
Magnetoencephalography (MEG) allows measurement of electrophysiological brain function, with high spatial and temporal resolution. However, traditional systems rely on superconducting sensors that require cryogenic cooling, making them large, expensive, and unsuitable for naturalistic experiments (e.g. where participants move). Optically-Pumped Magnetometers (OPMs) offer a transformative alternative (Schofield, 2023). These lightweight, non-cryogenic sensors can be placed closer to the scalp, improving signal quality (Boto, 2016). Moreover, OPMs are helmet mounted, allowing adaptation to different head sizes and (because sensors move with the head) free participant movement during scanning.
Despite their promise, existing OPM-MEG systems face limitations including low dynamic range and higher sensor noise than SQUIDs (Boto, 2022). The OPM array also requires control signals to be sent, and output signals received, independently yet synchronously, to and from each of the sensors; this requires complex control electronics which are often housed in large racks and require heavy cabling to the head mounted sensors. This reduces system robustness and the extensive cabling makes it difficult to conduct naturalistic experimental paradigms – for example where participants stand up, balance, or walk.
In this study, we demonstrate and validate a new platform for OPM-MEG (Neuro-1, QuSpin). This device is centred around a miniaturised, wearable electronics control unit which can be worn as a backpack, with minimal cabling. This design offers a route to realising the full potential of OPM-MEG as a means to undertake naturalistic neuroscientific experiments.
Despite their promise, existing OPM-MEG systems face limitations including low dynamic range and higher sensor noise than SQUIDs (Boto, 2022). The OPM array also requires control signals to be sent, and output signals received, independently yet synchronously, to and from each of the sensors; this requires complex control electronics which are often housed in large racks and require heavy cabling to the head mounted sensors. This reduces system robustness and the extensive cabling makes it difficult to conduct naturalistic experimental paradigms – for example where participants stand up, balance, or walk.
In this study, we demonstrate and validate a new platform for OPM-MEG (Neuro-1, QuSpin). This device is centred around a miniaturised, wearable electronics control unit which can be worn as a backpack, with minimal cabling. This design offers a route to realising the full potential of OPM-MEG as a means to undertake naturalistic neuroscientific experiments.
·Figure 1
Methods:
To evaluate the new Integrated Miniaturised (IM) OPM-MEG system, we conducted a comparative study with an established Rack-Mounted (RM) OPM-MEG system. System details are shown in Figure 1. Both systems used 64 triaxial QuSpin sensors (192 channels), with the key difference being the control electronics.
Two participants underwent six scanning sessions using each system. The experimental paradigm had two trial types: 1) Visual gratings (to evoke gamma (30-100 Hz) oscillations in visual cortex) and 2) Images of faces (to elicit evoked responses in fusiform cortex). In response to the onset of the grating, participants were also asked to make a button press response (to induce beta-band (13-30 Hz) modulation in sensorimotor cortex). We aimed to quantitatively assess the similarity of the measured MEG data from both the RM and IM systems.
In addition to miniaturised electronics, the IM system can operate in 'closed-loop' mode on all three axes of measurement. This ostensibly increases dynamic range. To test this, a phantom was used to generate brain like magnetic fields, while a matrix coil system integrated into the MSR simultaneously generated a variable background field between 0 nT and 8nT. To further test dynamic range, a single participant was scanned performing a right-handed figure abduction while moving from sitting-to-standing (during which the movement caused the head to pass through a large range of background magnetic fields).
Portability of our system was assessed by transporting the IM system between a lab in Nottingham, UK to a lab in Brussels, Belgium. Two groups of 5 healthy participants were scanned in both locations, using a simple finger-abduction task to evaluate beta band modulation in sensorimotor cortex.
Finally, current clinical guidelines for MEG in epilepsy require that MEG data are acquired simultaneously with EEG. We therefore integrated our IM system with an EEG device (Brain Products) to verify that the system was compatible.
Two participants underwent six scanning sessions using each system. The experimental paradigm had two trial types: 1) Visual gratings (to evoke gamma (30-100 Hz) oscillations in visual cortex) and 2) Images of faces (to elicit evoked responses in fusiform cortex). In response to the onset of the grating, participants were also asked to make a button press response (to induce beta-band (13-30 Hz) modulation in sensorimotor cortex). We aimed to quantitatively assess the similarity of the measured MEG data from both the RM and IM systems.
In addition to miniaturised electronics, the IM system can operate in 'closed-loop' mode on all three axes of measurement. This ostensibly increases dynamic range. To test this, a phantom was used to generate brain like magnetic fields, while a matrix coil system integrated into the MSR simultaneously generated a variable background field between 0 nT and 8nT. To further test dynamic range, a single participant was scanned performing a right-handed figure abduction while moving from sitting-to-standing (during which the movement caused the head to pass through a large range of background magnetic fields).
Portability of our system was assessed by transporting the IM system between a lab in Nottingham, UK to a lab in Brussels, Belgium. Two groups of 5 healthy participants were scanned in both locations, using a simple finger-abduction task to evaluate beta band modulation in sensorimotor cortex.
Finally, current clinical guidelines for MEG in epilepsy require that MEG data are acquired simultaneously with EEG. We therefore integrated our IM system with an EEG device (Brain Products) to verify that the system was compatible.
Results:
The new IM OPM-MEG system demonstrated robust performance: Across 42 experiments, average channel loss was minimal (3 ± 5 per session), mostly due to cable disconnections. Setup time was quick (~3 minutes), and the system was well tolerated by all of the participants.
In the comparative study (between IM and RM), gamma, beta, and evoked responses were consistent across both systems. The locations of largest beta modulation were within 10 mm and the locations of largest gamma modulation were within ~20–30 mm (the larger discrepancy for gamma was likely due to a large activation area within visual cortex elicited by the visual stimulus. Timecourse correlations were high: >0.75 when comparing individual runs and >0.9 for averaged data. Data are shown for a single subject in Figure 2.
Phantom experiments confirmed that closed-loop operation preserved sensor linearity in magnetic fields up to 8 nT background magnetic field (whereas for open-loop operation, linearity declined significantly with increasing field). A sitting-to-standing task revealed robust beta-band responses to movement of the fingers, despite background field shifts exceeding 1.5 nT. Figure 3 shows the beta-band response during a right handed finger abduction during movement.
Measurements in the two labs (in the UK and Belgium) showed a high degree of similarity (1 mm peak separation, 0.96 correlation). The spatial signature and peak source timecourse for the averaged activity at each site is shown in Figure 4.
Finally, we demonstrated the new hardware is compatible with EEG hardware through simultaneous EEG and OPM-MEG recordings. Expected beta-band and gamma-band responses were clear in both modalities.
In the comparative study (between IM and RM), gamma, beta, and evoked responses were consistent across both systems. The locations of largest beta modulation were within 10 mm and the locations of largest gamma modulation were within ~20–30 mm (the larger discrepancy for gamma was likely due to a large activation area within visual cortex elicited by the visual stimulus. Timecourse correlations were high: >0.75 when comparing individual runs and >0.9 for averaged data. Data are shown for a single subject in Figure 2.
Phantom experiments confirmed that closed-loop operation preserved sensor linearity in magnetic fields up to 8 nT background magnetic field (whereas for open-loop operation, linearity declined significantly with increasing field). A sitting-to-standing task revealed robust beta-band responses to movement of the fingers, despite background field shifts exceeding 1.5 nT. Figure 3 shows the beta-band response during a right handed finger abduction during movement.
Measurements in the two labs (in the UK and Belgium) showed a high degree of similarity (1 mm peak separation, 0.96 correlation). The spatial signature and peak source timecourse for the averaged activity at each site is shown in Figure 4.
Finally, we demonstrated the new hardware is compatible with EEG hardware through simultaneous EEG and OPM-MEG recordings. Expected beta-band and gamma-band responses were clear in both modalities.
·Figure 2
·Figure 3
·Figure 4
Conclusions:
Overall, the IM OPM-MEG platform represents a substantial step toward. We have demonstrated equivalence to an established system; robustness during movement (enabled by closed loop operation) and portability, as well as consistency in measurements across two sites. This system will find significant future utility, particularly in the study of brain activity during naturalistic tasks.
Modeling and Analysis Methods:
Methods Development
Novel Imaging Acquisition Methods:
MEG
Keywords:
MEG
Other - Optically-Pumped Magnetometers; Hardware
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2. Boto, E. (2016). On the potential of a new generation of magnetometers for MEG: A beamformer simulation study. PLoS One, 11(8), e0157655.
3. Boto, E. (2022). Triaxial detection of the neuromagnetic field using optically-pumped magnetometry: Feasibility and application in children. NeuroImage, 252, 119027.