Mihaela Gheorghiu and Eberhard Gersing

pp. 777 - 784

Abstract

Alterations of membrane structure and function are essential characteristics of cells undergoing
ischemia. Noninvasive monitoring of tissue alterations during ischemia and the estimation of the
reversibility domain (corresponding to organ capability to fully recover its functions after shifting back to
normal blood perfusion) are important for biomedical applications allowing better time management
during surgical interventions, especially in organ transplantation.
Due to it’s capability to reveal inhomogeneities, as well as it’s noninvasive character, impedance
spectroscopy was used for continuous monitoring of the progression of excised tissue samples during
ischemia. We have developed a fast, noninvasive, automated method for quantitative analysis of impedance
spectra of tissue samples, capable of revealing, through characteristic parameters (dispersion amplitudes,
time constants and distribution parameters) membrane based microscopic processes like the closure of
gap-junctions (a characteristic of the early alterations of ischemic tissues in the reversibility phase).
Microscopic and equivalent circuit modeling was used to probe the effect of closure of cell connections
and of changes in electrical properties of cell constituents on impedance spectra. We have developed a normalizing procedure emphasizing the pattern of ischemic alterations and enabling the comparison of
different data sets.