Design and fabrication for next generation Magnetoencephalography

Hill, Ryan (2021) Design and fabrication for next generation Magnetoencephalography. PhD thesis, University of Nottingham.

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Magnetoencephalography (MEG) is a functional neuroimaging technique which, via assessment of magnetic fields generated by neural current, probes human brain function with high spatial and temporal accuracy. Current state-of-the-art MEG systems use Superconducting QUantum Interference Devices (SQUIDs) to detect these magnetic fields, which are roughly a billion times smaller than the Earth’s magnetic field. However, these systems are expensive and rely on liquid helium to maintain superconductivity, which imposes significant limitations. The need for a thermally insulating vacuum between the participant’s head and the sensors means there is typically a 2-5 cm scalp-to-sensor distance. The sensors are also fixed in place in a one-size-fits-all helmet, and so the gap is inhomogeneous with the largest brain-to-sensor distances typically in frontal areas. This gap increases dramatically for individuals with small heads (e.g. infants). In addition, any movement greater than 5 mm relative to the static sensor array will significantly degrade data quality.

Recently, Optically-Pumped Magnetometers (OPMs) have been demonstrated as potential successors to SQUIDs for use in MEG. They operate at body temperature allowing direct placement on the scalp, both increasing the signal-to-noise ratio and removing movement constraints. The array can be adapted to any head shape and size, and the lack of cryogenics removes the high running costs of the system. These benefits should allow MEG to be more accessible to research and clinical groups around the world, and provide a more wide-scale uptake of MEG as a functional imaging modality.

This thesis aims to develop the first wearable whole-head OPM-MEG system. This system can be deployed across the lifespan, and enable motion robustness so participants can move freely during a scan. Through the design of a generic helmet (and accompanying methods for co-registration), we present a demonstration of our system in young children, teenagers, and adults alike, obtaining high fidelity MEG data in all participants. We present novel paradigms that exploit the motion robustness of a wearable OPM-MEG system, as well as the first demonstration of whole-head coverage, and a comparison to the current state-of-the-art.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Brookes, Matthew
Bowtell, Richard
Keywords: Magnetoencephalography, MEG, OPM-MEG, Functional Neuroimaging
Subjects: Q Science > QC Physics > QC501 Electricity and magnetism
R Medicine > RC Internal medicine > RC 321 Neuroscience. Biological psychiatry. Neuropsychiatry
Faculties/Schools: UK Campuses > Faculty of Science > School of Physics and Astronomy
Item ID: 64283
Depositing User: Hill, Ryan
Date Deposited: 08 Feb 2024 13:14
Last Modified: 08 Feb 2024 13:14

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