Effects of Tissue Dehydration on Optical Diffuse Reflectance and Transmittance in Ex Vivo Porcine Skin

Soft tissues are heterogeneous materials that may be considered mixtures of water, proteins, and cells. The high degree of mismatch in refractive index between these constituents causes tissues to be highly turbid media [1]. Mechanical optical clearing is a technique for reducing tissue scattering and improving light-based diagnostics and therapeutics. Mechanical optical clearing is performed using indentation to locally modify tissue optical response, and this effect has been shown to be reversible in vivo [2]. This effect is attributed to transient changes in tissue water distribution as a result of interstitial pore flow of water due to tissue compression. This leads to the hypothesis that tissue optical response is also correlated to the tissue’s state of hydration. The goal of this study was to investigate whether or not a difference in tissue water content produces a measurable difference in tissue optical response and to correlate that response with mechanical deformation. Both diffuse reflectance and transmittance were selected as extrinsic optical signals of interest.