Measuring tissue optical properties in vivo using reflectance-mode confocal microscopy and OCT

Steven L. Jacques, Ravikant Samatham, Niloy Choudhury, Yongji Fu, David Levitz

Research output: Chapter in Book/Report/Conference proceedingConference contribution

12 Scopus citations

Abstract

The ability to separately measure the scattering coefficient (μs [cm-1]) and the anisotropy (g) is difficult, especially when measuring an in vivo site that can not be excised for bench-top measurements. The scattering properties (μs and g) can characterize the ultrastructure of a biological tissue (nuclear size, mitochondra, cytoskeletion, collagen fibers, density of membranes) without needing an added contrast agent. This report describes the use of reflectance-mode confocal scanning laser microscopy (rCSLM) to measure optical properties. rCSLM is the same as optical coherence tomography (OCT) when the OCT is conducted in focus-tracking mode. The experimental measurement involves translating the depth of focus, Zf, of an objective lens, down into a tissue. As depth z increases, the reflected signal R decreases due to attenuation by the tissue scattering (and absorption, μa). The experimental data behaves as a simple exponential, R(z) = ρ exp(-μz f) where ρ is the local reflectivity (dimensionless) and μ [cm-1] is an attenuation coefficient. The relationship between (ρ,μ) and (μs,g) is: μ = (μs a(g) + μa)2 G(g,NA) ρ-μs Lf b(g,NA) where a(g) is a factor that drops from 1 to 0 as g increases from 0 to 1 (determined by Monte Carlo simulations) allowing photons to reach the focus despite scattering, G is a geometry factor describing the average photon pathlength that depends on the numerical aperture (NA) of the lens and the anisotropy (g), Lf is the axial extent of the focus, and b(g,NA) is the fraction of scattered light that backscatters into the lens for detection.

Original languageEnglish (US)
Title of host publicationBiomedical Applications of Light Scattering II
DOIs
StatePublished - Apr 21 2008
EventBiomedical Applications of Light Scattering II - San Jose, CA, United States
Duration: Jan 19 2008Jan 21 2008

Publication series

NameProgress in Biomedical Optics and Imaging - Proceedings of SPIE
Volume6864
ISSN (Print)1605-7422

Other

OtherBiomedical Applications of Light Scattering II
CountryUnited States
CitySan Jose, CA
Period1/19/081/21/08

Keywords

  • Confocal microscopy
  • Optical coherence tomography
  • Reflectance
  • Tissue optical properties

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Biomaterials
  • Atomic and Molecular Physics, and Optics
  • Radiology Nuclear Medicine and imaging

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  • Cite this

    Jacques, S. L., Samatham, R., Choudhury, N., Fu, Y., & Levitz, D. (2008). Measuring tissue optical properties in vivo using reflectance-mode confocal microscopy and OCT. In Biomedical Applications of Light Scattering II [68640B] (Progress in Biomedical Optics and Imaging - Proceedings of SPIE; Vol. 6864). https://doi.org/10.1117/12.761803