A modified boundary element method for the estimation of potential fields on the scalp

A modified boundary element method (BEM) for the calculation of potential fields on the scalp is proposed and tested in a three-shell model. The method greatly reduces the computational burden with only a small cost in accuracy. The resistivity of the skull is taken as infinite and the potential field on the inner skull surface is calculated using the standard BEM method for a one-surface system. Then the potential at any single selected point on the scalp is calculated directly from Green's theorem. The method does not give an accurate estimate of the magnitude of the potential on the scalp, but it does preserve correct relative magnitudes over all source locations in the head.