Modelling the human skull using FEM – effects of errors and simplifications

We used computer simulations to investigate finite element models [1] of the human skull in EEG source analysis. In the first part, we present a systematic investigation on the accuracy of different ways to account for the layered skull structure. We investigated local models, where each skull location was modeled differently, and global models, where the skull was assumed to be homogeneous, both using isotropic as well as anisotropic conductivity assumptions. We determined errors both in the forward calculation and the reconstructed dipole position [2]. In the second part, we investigate the effect of a number of common errors and limitations in skull modeling, using both forward and inverse simulations. Test models included erroneous skull holes, local errors in skull thickness, modeling cavities as compact bone, downward extension of the volume conductor and simplifying the inferior skull and the inferior skull and scalp as layers of constant thickness.