Describing head shape with surface harmonic expansions

A method is presented that uses a surface harmonic expansion to describe the shape of a head boundary. The coefficients of the expansion and the best fitting origin of the expansion are found by a nonlinear least-squares fit. This results in a compact representation of the shape of the head boundary. As with the 2-D and 3-D Fourier descriptions, once the coefficients are known, it is easy to construct triangular tessellations of any desired fineness. However, there is no requirement to sample the head in any particular sequence or at special angles. This facilitates calculation of the electric potential and magnetic field generated by neural current sources using discretized integral equations.