Portable and dynamic magnetoencephalography measurement using compact MSR by precise two-stage magnetic field...

The non-invasive technique of magnetoencephalography (MEG) has become increasingly vital for neuroscience research as well as for disease diagnosis and treatment. This article presents a portable and dynamic MEG system that utilizes a compact magnetically shielded room (MSR) integrated with a high-performance magnetic field compensation system and an MEG helmet equipped with an array of optically pumped magnetometer (OPM) sensors, achieving both high resolution and cost-effectiveness. The magnetic field compensation system employs two types of custom coils: external Helmholtz-like coils to adjust the distribution of residual magnetic fields, and internal planar coils to control magnetic field bias and disturbances. This configuration, combined with an active disturbance rejection control (ADRC) strategy, establishes an ultra-weak and stable measurement environment across a large uniform region. We then conducted experiments in which subjects wore the MEG helmet and underwent MEG measurements during periodic eye opening and closing and electrical median nerve stimulation, performed in both stationary and natural movement states. The above brain magnetic signals were measured in the occipital lobe and the postcentral gyrus, respectively. The results demonstrate that the MEG system maintains a comparable high detection resolution when the subject moves, while also offering significantly reduced cost and weight. The proposed system promises to deliver significant benefits for clinical practice and neuroscience research.