Improved measurement surface for MEG using magnetic-dipole sources and a spherical-multipole expansion

Abstract. The multipole representation of Magnetoencephalography (MEG) signals is known as a useful tool for distinguishing between magnetic fields arising from the brain and external disturbances. In this contribution we extend this concept and show that a closed double-layer surface with magnetometer probes is better suited to determine the corresponding multipole amplitudes α_lm than a conventional single-layer surface with gradiometers and magnetometer probes. For two different source configurations we show that the α_lm rapidly converge to the exact values. This proof of concept motivates to further optimize the geometry of the double-layer surface and the sensors' positions.