Misinterpretation of Scalp Voltage Response in the Application of Electrical Impedance Tomography to the Head

Abstract

ABSTRACT Electrical impedance tomography (EIT) is an imaging technique used for localizing impedance change by using boundary voltage information. In the application to the head, instead of using a reconstruction image for localization,scalp voltage response was used to roughly localize the response sources. In this study, the applicability of this approach to use scalp voltage for localizing neuronal sources was investigated. An inclusion was used to mimic the neuronal response. Two conventional EIT current-injection patterns, i.e. adjacent and opposite current injection were simulated. The results show that, in many cases, the location where the significant voltage response occurred was not the nearby location of the source of response. Almost all responses obtained from the adjacent injection pattern were misinterpreted. In the case of using the opposite injection pattern, the voltage response can be roughly used to localize the source of response, but not straightforwardly. The response obtained from the low-sensitivity regions and that obtained from the regions where a current injection electrode was situated and the source was not nearby were misinterpreted. However, the misinterpreted response of the latter region can be identified by determining the amplitude. Therefore, using the opposite pattern can roughly localize the source of response. This can be used for interpreting the scalp voltage response without the need for exhaustive work of image reconstruction. This also can be used as a guideline to interpret responses reported by previous studies and to design current and measurement configuration of EIT applications.