Mutual localization of electrode pairs in a 4-electrode measuring system

Abstract

The purpose of this study was to examine the transformation of a 2-electrode system into a 4-electrode system by gradually removing the current carrying (CC) electrode pair from the stationary signal pick-up (PU) pair. Both a Finite Element Method (FEM) analysis on a homogeneous tissue model and in-vivo measurements were used. We found that the general transfer impedance dependence on CC electrode distance was similar for the two methods. With the same excitation current the transfer impedance of a 4-electrode system may be measured with less than 1/10 of the signal amplitude obtained with a 2-electrode system. Also the transfer impedance spectra changed character. The admittance characteristic frequency of the alpha dispersions increased from 32 Hz to 160 Hz and beta dispersions decreased from 100 kHz to 13 kHz with increasing distance. © 2010 IOP Publishing Ltd.