Relationship between Deviations of Dipole Orientation and Position in MEG Topography

This study focuses on the influence of inhomogeneities in the human head on surface magnetic fields generated by radial dipoles inside the head. Using a simple inhomogeneous spherical model, components of magnetic fields perpendicular to the surface of the sphere are calculated, and the spatial distributions of MEGs are simulated. The influences of both rotation or inclination of the dipole orientation and shifting of the dipole position on the spatial distributions of MEGs were investigated. It is shown that when the dipole orientation is inclined from the radial direction, the spatial patterns of MEGs are analogous to the results when the dipole position is shifted. The effect of inhomogeneities of brain lesions on the spatial MEG patterns produced by radial dipoles is also studied.