Research Papers

Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers

[+] Author Affiliations
Rachel Estelle Thilwind, Gert ’t Hooft, Natallia E. Uzunbajakava

Philips Research, High Tech Campus 34, 5656 AE Eindhoven, The Netherlands

J. Biomed. Opt. 14(2), 024026 (March 24, 2009). doi:10.1117/1.3103339
History: Received November 06, 2008; Revised January 28, 2009; Accepted January 28, 2009; Published March 24, 2009
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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 1000to1940nm. 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 60deg. 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.

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© 2009 Society of Photo-Optical Instrumentation Engineers

Citation

Rachel Estelle Thilwind ; Gert ’t Hooft and Natallia E. Uzunbajakava
"Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers", J. Biomed. Opt. 14(2), 024026 (March 24, 2009). ; http://dx.doi.org/10.1117/1.3103339


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