New MEG technology for evaluating focal brain function

Abstract The synthetic aperture magnetometry (SAM) is a spatially selective beamformer, which transforms neuromagnetic signals into units of dipole moment on a per-voxel basis. We applied this technique to demonstrate the tomographic distribution of the power calculated from the spontaneous magnetoencephalogram (MEG) activities in a patient with a focal cerebral ischemia. The distribution of spontaneous MEG activity was affected by the changes in the regional cerebral blood flow (rCBF) and also by the presence of magnetic resonance image (MRI)-documented lesion. The present study for the first time demonstrated the altered patterns in the tomography of spontaneous MEG activity at different frequency bands, i.e. delta, alpha and beta bands, in a stroke patient which may elucidate an important implication in the pathoneurophysiology associated with cerebral ischemia.