Effect of Contact Impedance on the Head Electrical Properties Based on EIT Technology

Electrical impedance tomography (EIT) is a noninvasive technique that permits estimation of resistivity within a subject by reconstructing from boundary measurements. The head electrical properties based on EIT technology have been studied by many authors and in most of this work the realistic head model has been considered without contact impedance between the electrodes and the scalp. It is interesting to evaluate the effect of contact impedance on surface potential distributions because the contact impedance and the current density through this contact impedance are both high. In this paper we describe a complete electrode realistic head model that takes into account the presence of the electrode-scalp contact impedance. Using the finite element method (FEM), we get the surface potential distribution curves whose amplitude and shape are affected evidently by the magnitude of the contact impedance. The complete electrode realistic head model can be used to improve the precision of the reconstructed images by EIT