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.