INFLUENCE OF THE SCATTERING PHASE FUNCTION ON LIGHT TRANSPORT MEASUREMENTS IN TURBID MEDIA PERFORMED WITH SMALL SOURCE-DETECTOR SEPARATIONS

Many methods of optical tissue diagnosis require that measurements be performed with small source-detector separations in a backscatter geom etry. Monte Carlo simulations are used to demonstrate that for these s ituations light transport depends on the exact form of the angular sca ttering probability distribution, P(theta). Simulations performed with different forms of P(theta) with the same value of(cos theta) result in the collection of significantly different fractions of the incident photons, particularly when small-numerical-aperture delivery and coll ection fibers are employed. More photons are collected for the distrib ution that has a higher probability of scattering events with theta > 125 degrees. For the clinically relevant optical parameters employed h ere, the differences in light collection are >60%.