TY - JOUR
T1 - Improved depth resolution in near-infrared diffuse reflectance spectroscopy using obliquely oriented fibers
AU - Thilwind, Rachel Estelle
AU - 't Hooft, Gert
AU - Uzunbajakava, Natallia E.
PY - 2009
Y1 - 2009
N2 - 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.
AB - 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.
KW - depth selectivity
KW - diffuse reflectance
KW - Monte Carlo simulations
KW - near-infrared (NIR) spectroscopy
KW - oblique orientation
KW - penetration depth
UR - http://www.scopus.com/inward/record.url?scp=67650320851&partnerID=8YFLogxK
U2 - 10.1117/1.3103339
DO - 10.1117/1.3103339
M3 - Article
C2 - 19405755
AN - SCOPUS:67650320851
VL - 14
JO - Journal of Biomedical Optics
JF - Journal of Biomedical Optics
SN - 1083-3668
IS - 2
M1 - 024026
ER -