Field compensation for optically pumped magnetometer based magnetoencephalography

• Applicant: Dr.-Ing. Hermann Kutschka
• Subject Area: Biomedical Systems Technology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 541620223

While optically pumped magnetometers (OPMs) can be attached to the head of a person and allow for highly sensitive recordings of the human magnetoencephalogram (MEG), they are mostly limited to an operational range of approximately +-5 nT. Consequently, even inside a magnetically shielded room (MSR), movements in the remnant magnetic field disable the OPMs. Active suppression of the remnant field utilizing compensation coils is therefore essential. Recent achievements in our MEG lab and in other labs led to sophisticated compensation coil designs and corresponding coil control systems. In practice however, it remains a challenge to provide a sufficiently low absolute magnetic field environment for high-quality brain recordings. We propose a novel method for compensation coil designs based on an orthogonal decomposition of magnetic field vectors and surface currents. Moreover, in contrast to previously built MEG compensation coils, simultaneous compensation from coils inside and outside the MSR is proposed. The proposed coils will allow compensation of a higher number of field components and hence for the reduction of higher spatial orders in the remnant magnetic field. Consequently, the proposed coils will allow for larger head movements or smaller movement artifacts in future MEG experiments compared to existing coils. We hypothesize, that the proposed coil design will improve the signal-to-noise ratio of acquired MEG data compared to acquisitions with state-of-the-art coil designs. For the operation of our coils, a multi-channel, low-noise control system is proposed.

• DFG Programme: Research Grants
• Co-Investigators: Professor Dr.-Ing. Jens Haueisen; Dr. Burkhard Maess