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Journal of Biomedical Optics • Open Access

Estimating the absorption coefficient of the bottom layer in four-layered turbid mediums based on the time-domain depth sensitivity of near-infrared light reflectance
Author(s): Chie Sato; Miho Shimada; Yukari Tanikawa; Yoko Hoshi

Paper Abstract

Expanding our previously proposed “time segment analysis” for a two-layered turbid medium, this study attempted to selectively determine the absorption coefficient (μ a ) of the bottom layer in a four-layered human head model with time-domain near-infrared measurements. The difference curve in the temporal profiles of the light attenuation between an object and a reference medium, which are obtained from Monte Carlo simulations, is divided into segments along the time axis, and a slope for each segment is calculated to obtain the depth-dependent μ a (μ seg a ) . The reduced scattering coefficient (μ s ′ ) of the reference is determined by curve fitting with the temporal point spread function derived from the analytical solution of the diffusion equation to the time-resolved reflectance of the object. The deviation of μ seg a from the actual μ a is expressed by a function of the ratio of μ seg a in an earlier time segment to that in a later segment for mediums with different optical properties and thicknesses of the upper layers. Using this function, it is possible to determine the μ a of the bottom layer in a four-layered epoxy resin-based phantom. These results suggest that the method reported here has potential for determining the μ a of the cerebral tissue in humans.

Paper Details

Date Published: 20 September 2013
PDF: 9 pages
J. Biomed. Opt. 18(9) 097005 doi: 10.1117/1.JBO.18.9.097005
Published in: Journal of Biomedical Optics Volume 18, Issue 9
Show Author Affiliations
Chie Sato, The Tokyo Metropolitan Institute of Medical Science (Japan)
Miho Shimada, High Energy Accelerator Research Organization (Japan)
Yukari Tanikawa, National Institute of Advanced Industrial Science and Technology (Japan)
Yoko Hoshi, The Tokyo Metropolitan Institute of Medical Science (Japan)

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