A New Generation of Magnetoencephalography: Room Temperature Measurements using Optically-Pumped Magnetometers

Published

January 25, 2017

Author(s)

Elena Boto, Sofie S. Meyer, Vishal Shah, Orang Alem, Svenja A. Knappe, Peter Kruger, Mark Fromhold, Peter G. Morris, Richard W. Bowtell, Gareth R. Barnes, Matthew J. Brookes, Mark Lim

Abstract

Significant advances in the field of quantum sensing mean that magnetic field detectors, operating at room temperature, are now able to achieve sensitivity similar to that of cryogenically cooled devices (SQUIDs). This means that room temperature magnetoencephalography (MEG), with a greatly increased flexibility of sensor placement and dramatically lower cost, can now be considered. Furthermore, these new sensors can be placed directly on the scalp surface giving a theoretical 5-10 fold increase in the magnitude of the measured signal. Here, we present recordings made with a single Optically-Pumped Magnetometer (OPM) in combination with a 3D-printed head cast designed to accurately locate and orient the OPM. Because our OPM is configured as a magnetometer (as distinct from gradiometers) it is highly sensitive to environmental interference. However, we show that this problem can be ameliorated via the use of simultaneous reference sensor recordings and synthesised gradiometry. Following this, using median nerve stimulation, we show that our OPM can detect both evoked and induced changes when placed over sensory cortex; with signals exhibiting 6 times the magnitude and twice the signal-to-noise ratio (SNR) of equivalent metrics made using SQUIDs. Finally, we show that our OPM measurements, coupled with sub-millimetre accuracy in OPM placement (afforded by the head cast) allows for accurate localisation of the evoked response to somatosensory cortex. Our results highlight the unique opportunity to generate uncooled, potentially low-cost OPM-based MEG systems which offer a step change in sensitivity compared to the current generation instrumentation.

Citation

Neuroimage

Pub Type

Journals

Keywords

magnetoencephalography, MEG, optically-pumped magnetometers, OPM

Citation

Boto, E. , Meyer, S. , Shah, V. , Alem, O. , Knappe, S. , Kruger, P. , Fromhold, M. , Morris, P. , Bowtell, R. , Barnes, G. , Brookes, M. and Lim, M. (2017), A New Generation of Magnetoencephalography: Room Temperature Measurements using Optically-Pumped Magnetometers, Neuroimage (Accessed April 30, 2024)