Precision magnetic field modelling and control for wearable magnetoencephalography

•OPMs offer a step change for MEG, but rely on controlled magnetic field environments.•Here, optical tracking is combined with magnetometer data to create precision field maps.•Field maps are used to inform optimal currents in magnetic field cancellation coils.•The remnant static magnetic field experienced by the OPMs is reduced to 0.29 nT.•Motion artefact in OPM-MEG data is reduced by a factor of 5 via field nulling. Optically-pumped magnetometers (OPMs) are highly sensitive, compact magnetic field sensors, which offer a viable alternative to cryogenic sensors (superconducting quantum interference devices – SQUIDs) for magnetoencephalography (MEG). With the promise of a wearable system that offers lifespan compliance, enables movement during scanning, and provides higher quality data, OPMs could drive a step change in MEG instrumentation. However, this potential can only be realised if background magnetic fields are appropriately controlled, via a combination of optimised passive magnetic screening (i.e. enclosing the system in layers of high-permeability materials), and electromagnetic coils to further null the remnant magnetic field. In this work, we show that even in an OPM-optimised passive shield with extremely low (