Influence of path length on remote optical sensing of properties of biological tissue

A photon migration model is applied to the analysis of remote-sensing techniques that use light to probe the properties of biological tissues. Specific consideration is given to the effect of photon path length on the signals obtained from laser Doppler detection of blood flow in tissue microvasculature. We show how changes in blood volume or variation in spacing between delivery and detecting fibers might affect the measurements. We also examine how changes in path length can affect parameters determined by time resolved optical spectroscopy of blood oxygenation. Anisotropies in the angular distribution of scattered photons are taken into account.