Simple two-layer reflectance model for biological tissue applications: lower absorbing layer.

A simple two-layer tissue reflectance model is described. This work is a continuation of our investigations on modeling reflectance from two-layered tissues that we recently initiated. In the present article, we describe a variation of a two-layer model that assumes a lower absorbing and scattering layer and an upper scattering-only layer. This two-layer configuration is a realistic model for biological tissues in the visible and near-IR spectral ranges, where the upper layer may be an epithelial layer and the lower layer is a vascularized stroma layer. Application of the model yields estimates for tissue parameters, such as the thickness of the upper layer or the absorption properties of the lower layer. These parameters are of great interest for the noninvasive study of a wide range of epithelial biological tissues. The validity range and accuracy of the model are tested on tissue phantoms in both the forward and inverse modes of application.