Ex-vivo biological tissue differentiation by the Distribution of Relaxation Times method applied to Electrical Impedance Spectroscopy

We present the distribution of relaxation times (DRT) method applied to the electrical impedance spectrum data for improving the differentiation of biological tissues by means of two scenarios, a non-parametric representation and a parametric model. The complex electrical impedance from 1 kHz to 1 MHz was measured for ex-vivo WISTAR rat liver, heart, kidney, lung, muscle, and spleen tissues using a homemade electrical impedance spectroscopy (EIS) instrument and analyzed by the DRT method in a time constant domain revealing a particular non-parametric representation for differentiating each tissue using the retrieved distribution function. A larger number of relaxation time constants are found giving the possibility of studying the different polarization processes related to the tissues. We propose a parametric impedance model associated to DRT in the frequency domain to estimate the complex impedance of EIS measurements. Our results were compared with that obtained by the classical impedance Cole-Cole model.