Near-infrared spectroscopy of a heterogeneous turbid system containing distributed absorbers

Hanli Liu; Andreas H. Hielscher; Bertrand Beauvoit; Lihong V. Wang; Steven L. Jacques; Frank K. Tittel; Britton Chance

doi:10.1117/12.200817

31 January 1995 Near-infrared spectroscopy of a heterogeneous turbid system containing distributed absorbers

Hanli Liu, Andreas H. Hielscher, Bertrand Beauvoit, Lihong V. Wang, Steven L. Jacques, Frank K. Tittel, Britton Chance

Proceedings Volume 2326, Photon Transport in Highly Scattering Tissue; (1995) https://doi.org/10.1117/12.200817
Event: International Symposium on Biomedical Optics Europe '94, 1994, Lille, France

Abstract

In most biological tissues, absorbers such as blood in the blood vessels are localized within a low-absorbing background medium. To study the effect of distributed absorbers on the near infrared reflectance, we developed a Monte Carlo code and performed time-domain measurements on heterogeneous tissue-vessel models. The models were made of low absorbing polyester resin mixed with TiO₂ as scatters. A series of tubes with diameters of 3.2 or 6.4 mm were made in the resin sample. The volume ratio of the tubes to the total sample is about 20%. During the measurement, these tubes were filled with turbid fluids with different absorption coefficients to simulate blood in various oxygenation states. We found that the apparent absorption coefficient of the resin/tube system, determined by using the diffusion equation fit, can be approximated by a volume-weighted sum of the absorption coefficients of the different absorbing components. This approximation has to be replaced by a more complex expression if the difference in absorption between the absorbers and background is very large (approximately 20 times). The results of the tissue phantom study are supported by the Monte Carlo simulation. Possible explanations for the photon migration in this kind of heterogeneous system is also presented.

Citation Download Citation

Hanli Liu, Andreas H. Hielscher, Bertrand Beauvoit, Lihong V. Wang, Steven L. Jacques, Frank K. Tittel, and Britton Chance "Near-infrared spectroscopy of a heterogeneous turbid system containing distributed absorbers", Proc. SPIE 2326, Photon Transport in Highly Scattering Tissue, (31 January 1995); https://doi.org/10.1117/12.200817

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