title: Measurement of dye diffusion in scattering tissue phantoms using dual-wavelength low-coherence interferometry.
abstract: We demonstrate low-coherence interferometry (LCI) for dye diffusion measurements in scattering tissue phantoms. The diffusion coefficient of a phthalocyanine dye in 1.5% agar gel containing scattering Intralipid was measured using a dual-wavelength interfero-meter. One wavelength was matched to the absorption peak of the dye at 675 nm. The other, 805 nm, was not affected by the dye, and was used to correct for varying sample scattering as a function of depth, assuming a constant ratio between scattering at the two wavelengths. The same wavelength dependence of scattering is assumed for the entire sample, but no a priori knowledge about the amount of scattering is needed. The dye diffusion coefficient was estimated by fitting a mathematical model of the interferometer signal to the measured LCI envelope. We compare results obtained using both a constant-scattering and a depth-resolved-scattering approach to determine the sample scattering. The presented method provides robust estimation of the diffusion coefficient when spatial resolution in determining the depth-resolved scattering is varied. Results indicate that the method is valid for samples having continuous spatial variations in the scattering coefficient over lengths as short as the coherence length of the probing light. The method allows in situ characterization of diffusion in scattering media.
authors.affiliation: Norwegian University of Science and Technology, Department of Physics, N-7491 Trondheim, Norway.
authors.forename: Trude
authors.initials: T
authors.lastname: Storen
authors.forename: Arne
authors.initials: A
authors.lastname: Royset
authors.forename: Lars O
authors.initials: LO
authors.lastname: Svaasand
authors.forename: Tore
authors.initials: T
authors.lastname: Lindmo
mesh_terms: D000818:Animals; D016477:Artifacts; D003198:Computer Simulation; D003238:Connective Tissue / Q000737:chemistry*; D004058:Diffusion; D005217:Fat Emulsions, Intravenous / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000032:analysis / Q000737:chemistry*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007368:Interferometry / Q000295:instrumentation* / Q000379:methods; D036641:Microscopy, Fluorescence, Multiphoton / Q000295:instrumentation* / Q000379:methods; D008954:Models, Biological; D008956:Models, Chemical; D012542:Scattering, Radiation; D014018:Tissue Distribution; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods
chemical_list: D005217:Fat Emulsions, Intravenous; D005456:Fluorescent Dyes