A portable
magnetoencephalography (MEG)
system (100) for non-invasive recording of magnetic fields of the brain during natural behaviors, the
system (100) comprising: an adaptable non-ferromagnetic helmet (1) configured to be worn on the head of a
test subject; a plurality of interchangeable sensor capsules (2) attached to the helmet (1), each sensor
capsule (2) comprising: a triaxial
quantum magnetometer (3) in the form of an optically pumped
magnetometer configured to measure magnetic fields along three orthogonal axes, and a local
inertial measurement unit (IMU) (4) configured to provide motion signals with
six degrees of freedom; at least one additional IMU (5) attached to the helmet (1) and configured to measure
head movements; an active field control subsystem (6) comprising a plurality of
magnetic field generating coils (7) embedded in the helmet (1) and at least one reference
quantum magnetometer (8) positioned to detect magnetic fields in the environment; an external electronic module (9) containing at least one
clock generator (25), at least one
digital processor (26), at least one power supply circuit and a
wireless communication interface (19); a weak magnetic connection (10) between the sensor capsules (2) and the external
electronics module (9), wherein the weak magnetic connection (10) comprises at least one optical wiring and / or one non-ferromagnetic
electrical wiring; and a
control unit (11) that is connected to the sensor capsules (2), the reference
quantum magnetometer (8), the IMUs (4, 5), the active field control subsystem (6) and the external
electronics module (9), wherein the helmet (1) and the sensor capsules (2) are configured to maintain a sensor-to-
scalp distance of less than or equal to 10 mm over a range of head sizes, and the
control unit (11) is configured that they: (i) to synchronize the magnetometer signals from the triaxial quantum magnetometers (3) and the IMU signals from the IMUs (4, 5) with a synchronization error of no more than 0.5 ms, (ii) continuous updating of the conduction fields that map the brain sources to the sensor capsules (2) based on the IMU signals from the IMUs (4, 5), and (iii) to reconstruct the magnetic activity of the brain in real time using the updated conduction fields while the
test subject performs voluntary movements.