Estimation of Dielectric Property for Biological Tissues by Multi-Frequency Approximation

Abstract

This paper investigates a new method to calculate the dielectric property (DP) of biological tissues with the open-ended coaxial probes (OECP). The DP of tissues is a continuous function of frequency which can be represented with different dielectric relaxation models. Thus, the accuracy of DP measurements can be increased by enforcing such spectral continuity using the Cole-Cole model. A cost functional based on an admittance integral was calculated at the tip of the OECP. Then, Cole-Cole parameters <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\epsilon_{\infty}, \epsilon_{s}, \tau, \alpha$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\sigma)$</tex> were applied into the admittance integral to solve a set of nonlinear equations. The OECP, biological tissues and calibration materials were simulated using Ansys HFSS simulation program from 0.5 to 6 GHz frequency range with 0.25 GHz steps (23 frequency points). Finally, the accuracy of results was compared with data obtained from literature.