Time-Resolved Photon Propagation in Tissues

Photon movement in a turbid medium such as biological tissue has posed challenging problems due to the strong influence of light scattering at ultraviolet, visible, and near-infrared wavelengths. Photons which escape from a tissue as either reflectance or transmittance may have propagated along many different paths within the tissue. Therefore, it is difficult to interpret the magnitude of photon escape in terms of either tissue absorption or the presence of an internal heterogeneity. The use of measurement techniques which allow time-resolved measurements of photons has offered a new approach toward understanding photon propagation.