Interference suppression techniques for OPM-based MEG: Opportunities and challenges

  title={Interference suppression techniques for OPM-based MEG: Opportunities and challenges},
  author={Robert A. Seymour and Nicholas Alexander and Stephanie Mellor and George C. O’Neill and Tim M. Tierney and Gareth R. Barnes and Eleanor A. Maguire},
One of the primary technical challenges facing magnetoencephalography (MEG) is that the magnitude of neuromagnetic fields is several orders of magnitude lower than interfering signals. Recently, a new type of sensor has been developed - the optically pumped magnetometer (OPM). These sensors can be placed directly on the scalp and move with the head during participant movement, making them wearable. This opens up a range of exciting experimental and clinical opportunities for OPM-based MEG… 


Multi-Channel Whole-Head OPM-MEG: Helmet Design and a Comparison with a Conventional System
A wearable OPM-MEG system with ‘whole-head’ coverage based upon commercially available OPMs is constructed, and its capabilities to measure alpha, beta and gamma oscillations are tested, showing signal detection for the device to be highly robust and performance comparable to established cryogenic devices.
On the Potential of a New Generation of Magnetometers for MEG: A Beamformer Simulation Study
The results imply that the realisation of a viable whole-head multi-channel OPM system could generate a step change in the utility of MEG as a means to assess brain electrophysiological activity in health and disease, however in practice this will require both improved hardware and modelling algorithms.
Using OPMs to measure neural activity in standing, mobile participants
This proof-of-concept study sought to push the movement limits of OP-MEG even further and recorded auditory evoked fields while participants were standing up and continually moving their head, suggesting that a wide range of movement is possible with current OP- MEG systems.
Novel Noise Reduction Methods
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On-scalp MEG system utilizing an actively shielded array of optically-pumped magnetometers
In a conventional two-layer magnetically shielded room, the coil system reduced the maximum remanent DC-field component within an 8-channel OPM array from 70 to less than 1 nT, enabling the sensors to operate in the sensitive spin exchange relaxation-free regime.
Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working human brain
Magnetoencephalography (MEG) is a noninvasive technique for investigating neuronal activity in the living human brain. The time resolution of the method is better than 1 ms and the spatial
Spatiotemporal signal space separation method for rejecting nearby interference in MEG measurements.
Practical examples with artificial current dipoles and interference sources as well as data from real patients demonstrate that the spatiotemporal signal space separation method removes the artefacts without altering the field patterns of the brain signals.
Measuring functional connectivity with wearable MEG
This demonstration shows that a nascent OPM-MEG system offers results similar to a cryogenic device, even despite having ∼5 times fewer sensors, adding weight to the argument that OPMs will ultimately supersede cryogenic sensors for MEG measurement.
Non-Invasive Functional-Brain-Imaging with an OPM-based Magnetoencephalography System
It is anticipated that future OPM-based MEG systems will offer enhanced spatial resolution as they will capture finer spatial features compared to traditional MEG system employing SQUIDs.
Magnetic Field Mapping and Correction for Moving OP-MEG
The spatial variation in the magnetic field is model and use the model to predict the movement artefact found in a dataset and a large reduction in movement noise was achieved when this model was applied to OP-MEG data.