Modeling layered biological media: application to skin dielectric measurements

R. M. IRASTORZA; F. VERICAT; J. R. GRIGERA

Rosario

Congreso; XXXV Reunión Anual de la Sociedad Argentina de Biofísica; 2006

Sociedad Argentina de Biofísica

The present study compares three models, used to dielectrically represent non­invasive measurements in a layered biological media. It is useful in modeling skin dielectric measurements and deeper tissues. We generalize the empirical model to a four layered media and apply the results to the model of reference. Our work is focused on detecting the  relaxation processes from beta­ and gamma dispersions. Therefore we test and calibrate the models with phantom measurements in reference materials, using Time Domain Reflectometry (TDR) with a fast rise time (40pseg) step voltage. A novel application of a method of System Identification (SI), from signal processing theory, is used to analyze the experimental data. In reference TDR is also used, but a time domain physical model approach is applied to obtain the frequency response. Instead of this, in our study due to the SI technique, the frequency response is obtained  directly of the identified linear model. We conclude that the procedure is very fast and easy to apply for any sample, therefore it is a promising method for in vivo measurements of biological tissues, especially in skin. The measurement needs only a touch of the probe on a sample spot. Simulations with literature values are performed to study the sensitivity of our methodology and the validity of the physical models. We also conclude that there is a good agreement between the experimental data and the theoretical ones.