Instrumentation for low frequency EIT studies of the human head and its validation in phantom experiments

Abstract

We describe instrumentation for low frequency (< 500 Hz) EIT studies of the human head and its calibration, testing and validation in the phantom experiments. Our EIT system prototype is based on a 256 channel commercial EEG system complimented by the current injection module and lock-in detection software. We have designed and built two types of head phantoms: i) a resistor network and ii) a cylinder tank filled with saline and gel insertions with chemically targeted conductivity values. We have developed a technology for fabricating, handling and storage of agar TX151 gel insertions. Independent and direct conductivity measurements of gel samples have been performed using a HP LCR meter in a four electrode conductivity cell specifically designed and built for this purpose. Measurements of saline conductivity were done with commercially available salinity / conductivity meters. Our inverse conductivity estimates in the phantom experiments with EIDORS and in-house software cross-validate the viability of the EIT-EEG system. © 2010 IOP Publishing Ltd.