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29 July 2003 Quantitative estimate of spatial/temporal variations in the optical properties of tissue-like media from diffuse reflectance data
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Abstract
We have measured relative diffuse reflectance images on tissue-like liquid phantoms using a laser diode (784 nm, 40 mW) as a broad-beam source and a CCD camera detector. We have found that, to a good approximation, the result that the reflectance R only depends on the ratio of the absorption and reduced scattering coefficients of the medium (μas') can be extended to geometrical configurations that are more general than those considered by theoretical studies. In fact, over the range 0.0028<μas'<0.058 considered by us, the dependence of R on μas' varies by no more than 8% by changing the incidence angle of illumination over the range 0-30°. The relative diffuse reflectance vs. μas was well described by introducing an arbitrary normalization factor K in the analytic relationship for the absolute reflectance reported by S.L. Jacques [http://omlc.ogi.edu/news/may99/rd/index.html]: R=Kexp{-7.8/[3(1+μs'/μa)]}. The ratio of the relative diffuse reflectance values at two locations (for spatial changes) or at two times (for temporal changes) cancels out the unknown normalization factor K, so that this ratio can be used to obtain quantitative estimates of the corresponding change in μas'. We have experimentally estimated that in our experimental conditions R is sensitive to a superficial volume about 2 mm deep and 4 mm wide.
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Francesco Fabbri, Maria-Angela Franceschini, and Sergio Fantini "Quantitative estimate of spatial/temporal variations in the optical properties of tissue-like media from diffuse reflectance data", Proc. SPIE 4955, Optical Tomography and Spectroscopy of Tissue V, (29 July 2003); https://doi.org/10.1117/12.478167
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