Near infrared spectroscopy of a heterogeneous turbid system containing distributed absorbers

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

Research output: Contribution to journalConference article

6 Scopus citations

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 (∼ 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 systems are also presented.

Original languageEnglish (US)
Pages (from-to)164-172
Number of pages9
JournalProceedings of SPIE - The International Society for Optical Engineering
Volume2326
DOIs
StatePublished - Jan 31 1995
EventPhoton Transport in Highly Scattering Tissue 1994 - Lille, France
Duration: Sep 6 1994Sep 10 1994

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering

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