This module of the VTS allows the user to select the desired:
- source and detector configurations,
- tissue geometry, and
- radiative transport properties.
A special feature of this layer is the ability to define the radiative transport properties of the tissue either (a) conventionally in terms of the optical coefficients for absorption (μa) and scattering (μs) as well as, if appropriate, moments of the scattering phase function (g1,g2,.,gn) OR (b) in terms of tissue morphology and composition. This latter feature will queries the user about the tissue composition i.e., relative content of cells, extra cellular matrix, and vasculature as well as the concentration of important optical chromophores e.g., oxy- and deoxy-hemoglobin, water, melanin, fat, etc. From this user specification of tissue morphology and composition the VTS will automatically calculate the relevant optical properties at the desired wavelengths. A graphical representation of the capabilities resident in the Problem Definition Layer is provided below: