Time-Domain Electromagnetic Inversion Technique for Biological Tissues by Reconstructing Distributions of Cole-Cole Model Parameters

摘要

The Cole-Cole (C-C) models have been frequently used for a precise description of the dispersion characteristics of biological tissues. One of the main difficulties in the direct reconstruction of these dielectric properties from time-domain measurements is their frequency dependence. In order to overcome this difficulty, an electromagnetic (EM) inversion technique in the time domain is proposed, in which four kinds of frequency-independence model parameters, the optical relative permittivity, the static conductivity, the relative permittivity difference, and the relaxation time, can be determined simultaneously. It formulates the inversion problem as a regularized minimization problem, whose forward and backward subproblems could be solved iteratively by the finite-difference time-domain (FDTD) method and any conjugate gradient algorithm, respectively. Numerical results on two types of stratified C-C slabs, with smooth and discontinuous parameter profiles, respectively, confirm the performance of the inversion methodology.