Retrieval of the optical properties of a semiinfinite compartment in a layered scattering medium by single-distance, time-resolved diffuse reflectance measurements

- Modified model for light diffusion in infinitely thick N-layered cylinders, simpler than its finite counterpart.
- Fabrication of a three-layered phantom, where absorption changes in the last layer occur.
- Validation of the model by development of fitting algorithm used on phantom experiments and Monte Carlo simulations.

Functional analysis of the human brain requires methods that take the layered structure of the head into account. In this work we introduce an improved theoretical model that describes light propagation in multilayered, turbid cylinders with a infinitely thick bottom layer, which simplifies calculations and reduces computation times. Our approach was validated with Monte Carlo simulations and single distance, time-resolved experiments on a three-layered phantom, where the absorption of the deepest layer was gradually modified. We were able to retrieve both, the scattering and absorption coefficient of this layer within reasonable errors. Hereby, changes in scattering were found to have less effect on the experimental data than absorption changes, making the reliable estimation of the reduced scattering coefficient more difficult in comparison to absorption. Stability of the implemented fitting routine was thoroughly analyzed, revealing that special care is needed to obtain accurate values for the reduced scattering coefficient.