Sensitivity validation of a coaxial probe for a multilayer tissue model, using simulation and phantom measurements

Abstract

Dehydration is a covert disease state widely affecting the elderly, but no methods exist to sensitively and practically detect dehydration in non-clinical settings. In this thesis, a GHz-range noninvasive skin-contact coaxial probe measurement approach is proposed as a means to detect dehydration-linked changes in local skin water content. Prior studies have shown the sensitivity of such a measurement to changing water content of a material under test (MUT). This study aims to characterize the sensitivity of the probe to water content in the deeper dermal skin layer, below the epidermis. First, we develop a tissue bilayer model for skin whose main parameters of interest are water content and layer thickness, and characterize the coaxial probe's sensitivity to water content given different parameters of the lower layer of the model. We use in vitro tissue model measurements using the coaxial probe, and FEM simulation of an equivalent design, to determine the sensitivity of our coaxial probe. We have found that the sensing depth of the probe is at least 1mm in vitro. Current simulation results do not accurately reflect the in vitro measurements. The in vitro results support a conclusion that the coaxial probe can detect changes in water content of the dermis of the skin.