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Journal of Biomedical Optics

Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers
Author(s): Rachael Estelle Thilwind; Gert W. t'Hooft; Natallia Uzunbajakava
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Paper Abstract

We demonstrate a significant improvement of depth selectivity when using obliquely oriented fibers for near-infrared (NIR) diffuse reflectance spectroscopy. This is confirmed by diffuse reflectance measurements of a two-layer tissue-mimicking phantom across the spectral range from 1000 to 1940 nm. The experimental proof is supported by Monte Carlo simulations. The results reveal up to fourfold reduction in the mean optical penetration depth, twofold reduction in its variation, and a decrease in the number of scattering events when a single fiber is oriented at an angle of 60 deg. The effect of reducing the mean optical penetration depth is enhanced by orienting both fibers inwardly. Using outwardly oriented fibers enables more selective probing of deeper layers, while reducing the contribution from surface layers. We further demonstrate that the effect of an inward oblique arrangement can be approximated to a decrease in fiber-to-fiber separation in the case of a perpendicular fiber arrangement. This approximation is valid in the weak- or absorption-free regime. Our results assert the advantages of using obliquely oriented fibers when attempting to specifically address superficial tissue layers, for example, for skin cancer detection, or in noninvasive glucose monitoring. Such flexibility could be further advantageous in a range of minimally invasive applications, including catheter-based interventions.

Paper Details

Date Published: 1 March 2009
PDF: 9 pages
J. Biomed. Opt. 14(2) 024026 doi: 10.1117/1.3103339
Published in: Journal of Biomedical Optics Volume 14, Issue 2
Show Author Affiliations
Rachael Estelle Thilwind, Philips Research Nederland B.V. (Netherlands)
Gert W. t'Hooft, Philips Research Nederland B.V. (Netherlands)
Natallia Uzunbajakava, Philips Research Nederland B.V. (Netherlands)

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