EEG/MEG error bounds for a static dipole source with a realistic head model

We derive Cramer-Rao bounds (CRBs) on the errors of estimating the paramete rs (location and moment) of a static current dipole source using data from electro-encephalography (EEG), magneto-encephalography (MEG), or the combin ed EEG/MEG modality. We use a realistic head model based on knowledge of su rfaces separating tissues of different conductivities obtained from magneti c resonance (MR) or computer tomography (CT) imaging systems. The electric potentials and magnetic held components at the respective sensors are funct ions of the source parameters through integral equations. These potentials and Field are formulated for solving them by the boundary or the finite ele ment method (BEM or FEM) with a weighted residuals technique. We present a unified framework for the measurements computed by these methods that enabl es the derivation of the bounds. The resulting bounds may be used, for inst ance, to choose the best configuration of the sensors for a given patient a nd region of expected source location. Numerical results are used to demons trate an application for showing expected accuracies in estimating the sour ce parameters as a function of its position in the brain, based on real EEG /MEG system and MR or CT images.