Abstract. Single fiber reflectance spectroscopy is a method to noninvasively quantitate tissue absorption and scattering properties. This study utilizes a Monte Carlo (MC) model to investigate the effect that optical properties have on the propagation of photons that are collected during the single fiber reflectance measurement. MC model estimates of the single fiber photon path length (L_SF) show excellent agreement with experimental measurements and predictions of a mathematical model over a wide range of optical properties and fiber diameters. Simulation results show that L_SF is unaffected by changes in anisotropy (g [0.8, 0.9, 0.95]), but is sensitive to changes in phase function (Henyey–Greenstein versus modified Henyey–Greenstein). A 20% decrease in L_SF was observed for the modified Henyey–Greenstein compared with the Henyey–Greenstein phase function; an effect that is independent of optical properties and fiber diameter and is approximated with a simple linear offset. The MC model also returns depth-resolved absorption profiles that are used to estimate the mean sampling depth (Z_SF) of the single fiber reflectance measurement. Simulated data are used to define a novel mathematical expression for Z_SF that is expressed in terms of optical properties, fiber diameter and L_SF. The model of sampling depth indicates that the single fiber reflectance measurement is dominated by shallow scattering events, even for large fibers; a result that suggests that the utility of single fiber reflectance measurements of tissue in vivo will be in the quantification of the optical properties of superficial tissues.

Print publication: Issue 22 (21 November 2009)
Received 9 July 2009, in final form 14 October 2009
Published 4 November 2009