Experimental tests of a two-layer Monte Carlo - Diffusion hybrid model for photon migration in the frequency domain

We examine the ability to recover the optical properties of a two-layer turbid medium using multi-distance frequency domain reflectance measurements and a hybrid Monte Carlo - diffusion model. Frequency domain measurements are performed on two-layer liquid tissue phantoms simulating skin on muscle and skin on fat. Particular care to systematic effects in the photomultiplier is required for the measurements at short source-detectors distances. The model converges when fitting five free parameters (the optical properties of the upper and lower layers and the upper layer thickness). However, discrepancies between experiment and model yield insufficient accuracy for the absorption coefficicnt of the upper layer.