On-Scalp MEG

Book chapter, 2019

The development of new magnetic sensor technologies with relaxed thermal insulation requirements as compared to conventional magnetoencephalography (MEG) sensors has led to the birth of the field of on-scalp MEG, where sensor systems are flexibly placed directly on the scalp surface. Such improved proximity between the sensors and the brain has been theoretically demonstrated to boost signal levels and neuroimaging spatial resolution. Since the first on-scalp MEG measurements in 2012, a number of studies have experimentally verified these advantages with the two leading sensor technologies, namely, high criticaltemperature SQUIDs (high-Tc SQUIDs) and optically pumped magnetometers (OPMs). Current challenges being addressed that are specific to on-scalp MEG include relatively high sensor noise levels (specifically for high-Tc SQUIDs), limited bandwidth (specifically for OPMs), co-registration of a flexible sensor array, increased sensor crosstalk due to the denser spatial sampling required for improved spatial resolution, and engineering of a full-head system. The prospect for discovery of a neuroimaging challenge that on-scalp MEG uniquely solves is likely to push development further and possibly initiate utilization to a similar-or larger-scale as conventional MEG has reached today.