A New Noninvasive Method for Determining the Conductivity of Tissue Embedded in Multilayer Biological Structure

Abstract

A significant conductivity difference between normal and tumorous biological tissue has been reported in the literature. Such a conductivity difference makes it possible to diagnose the pathological tissue by measuring the change of tissue conductivity. A new noninvasive method is proposed to determine the conductivity of tissue embedded in a stratified biological structure. An open-ended coaxial line is used to measure the reflection coefficient of the structure, and then the conductivity of the tissue of interest can be obtained making use of an inverse calculation based on Genetic Algorithm (GA). To explore the feasibility of the proposed method, a numerical simulation is presented in this paper. In the simulation, the field distribution near the end of the coaxial line is computed making use of finite-difference time-domain (FDTD) method. Also, FDTD is employed to calculate the reflection coefficient from preset tissue conductivity, and then the forward-calculated reflection coefficient plus random noise is used to simulate the measured reflection coefficient. From the "measured" reflection coefficient, the tissue conductivity is obtained by a GA inverse calculation. Such calculated tissue conductivity is compared with its preset value to validate the accuracy of the proposed method. Also, the sensitivity of the reflection coefficient corresponding to the tissue conductivity change is investigated at different operating frequencies, and an optimal frequency is explored for maximum measurement sensitivity. The results of the numerical simulation verify the feasibility of the proposed new method, which has a potential application for cancer detection.