FINITE-ELEMENT MODELING OF ELECTRODE SKIN CONTACT IMPEDANCE IN ELECTRICAL-IMPEDANCE TOMOGRAPHY

In electrical impedance tomography (EIT), we inject currents through a nd measure voltages from an array of surface electrodes. The measured voltages are sensitive to electrode-skin contact impedance because the contact impedance and the current density through this contact impeda nce are both high. We used large electrodes to provide a more uniform current distribution and reduce the contact impedance. A large electro de differs from a point electrode in that it has shunting and edge eff ects which cannot be modeled by a single resistor. We used the finite element method (FEM) to study the electric field distributions underne ath an electrode, and developed three models: a FEM model, a simplifie d FEM model and a weighted load model. We showed that the FEM models c onsidered both shunting and edge effects and matched closely the exper imental measurements. FEM models for electrodes can be used to improve the performance of an electrical impedance tomography reconstruction algorithm.