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14 October 2015 On the geometry dependence of differential pathlength factor for near-infrared spectroscopy. I. Steady-state with homogeneous medium
Daqing Piao, Randall L. Barbour, Harry L. Graber, Daniel C. Lee M.D.
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Journal of Biomedical Optics, Vol. 20, Issue 10, 105005 (October 2015). https://doi.org/10.1117/1.JBO.20.10.105005
Abstract
This work analytically examines some dependences of the differential pathlength factor (DPF) for steady-state photon diffusion in a homogeneous medium on the shape, dimension, and absorption and reduced scattering coefficients of the medium. The medium geometries considered include a semi-infinite geometry, an infinite-length cylinder evaluated along the azimuthal direction, and a sphere. Steady-state photon fluence rate in the cylinder and sphere geometries is represented by a form involving the physical source, its image with respect to the associated extrapolated half-plane, and a radius-dependent term, leading to simplified formula for estimating the DPFs. With the source-detector distance and medium optical properties held fixed across all three geometries, and equal radii for the cylinder and sphere, the DPF is the greatest in the semi-infinite and the smallest in the sphere geometry. When compared to the results from finite-element method, the DPFs analytically estimated for 10 to 25 mm source–detector separations on a sphere of 50 mm radius with μa=0.01  mm−1 and μs′=1.0  mm−1 are on average less than 5% different. The approximation for sphere, generally valid for a diameter ≥20 times of the effective attenuation pathlength, may be useful for rapid estimation of DPFs in near-infrared spectroscopy of an infant head and for short source–detector separation.
CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.
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Daqing Piao, Randall L. Barbour, Harry L. Graber, and Daniel C. Lee M.D. "On the geometry dependence of differential pathlength factor for near-infrared spectroscopy. I. Steady-state with homogeneous medium," Journal of Biomedical Optics 20(10), 105005 (14 October 2015). https://doi.org/10.1117/1.JBO.20.10.105005
Published: 14 October 2015
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Cited by 28 scholarly publications.
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KEYWORDS
Sensors
Spherical lenses
Optical spheres
Diffusion
Finite element methods
Near infrared spectroscopy
Scattering
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