Study into the repeatability of the electrode-skin interface utilizing electrodes commonly used in electrical impedance tomography

Abstract

The possibility of un-quantified errors at the electrode-skin interface remains a key challenge to Electrical Impedance Tomography (EIT). The paper defines three sources of potential error in measurements that may be taken as part of a clinical EIT protocol. Experiments using the HP Impedance analyzer show the effect on measurement error that may result from these error sources. The findings show that the error among three materials of electrode used (Stainless Steel, Copper and Copper with gold plating) and between two types of electrode-skin contact methods, could produce higher error with using 'dry' electrode and low variation with 'wet' electrodes [patent], contact drift and electrode mismatching studies respectively for the 'dry' electrode is large, for the 'wet' electrode is small as well. Such errors offer a number of challenges for EIT imaging both when repeating measurements at different clinical visits and even at the same visit if either different electrode materials are used, or different electrode-skin contact methods are employed. The paper proposes a "best practice" to reduce these errors to the minimum possible. However continue residual errors continue to affect the detection capabilities of EIT. The Leicester Group is continuing the investigation to reduce these errors trough an optimisation of electrode design and the electrode-skin interface. © Springer-Verlag 2007.