Dielectric properties of rat liver in vivo: a noninvasive approach using an open-ended coaxial probe at audio/radio frequencies

To characterize the passive electrical properties of liver cells in vivo, w e measured the frequency dependence of relative permittivity and conductivi ty for rat liver lobes in situ by means of a noninvasive surface probe coup led with a fast impedance analyzer, covering the frequency range 10(2)-10(8 ) Hz. Securing a stable contact, mechanical as well as electrochemical, bet ween the probe and tissue surface both wetted with physiological saline, ma de it possible to collect a highly reproducible set of data even from lobes undergoing respiratory movement in situ. The data obtained traced a broad dielectric dispersion curve over the range 10(3)-10(8) Hz, suggestive of th e involvement of widely distributed relaxation times. As its theoretical an alyses based on cell membrane models are made in a companion paper [V. Raic u, T. Saibara, H. Enzan, A. Irimajiri, Dielectric properties of rat liver i n vivo: analysis by modeling hepatocytes in the tissue architecture, Bioele ctrochem. Bioenerg. 47 (1998) 333-342.], this report describes experimental conditions required for reliable measurements on a well-defined superficia l region of viable liver lobes. The most important factors among these are the tissue surface condition such as 'wet' or 'dry' and the effective penet ration depth of field lines defined by the probe's geometric characteristic s. (C) 1998 Elsevier Science S.A. All rights reserved.