Research Papers

Oblique-incidence illumination and collection for depth-selective fluorescence spectroscopy

[+] Author Affiliations
T. Joshua Pfefer, Anant Agrawal

Food and Drug Administration FDA/CDRH/HFZ-130, Center for Devices and Radiological Health, 12725 Twinbrook Parkway, Rockville, Maryland 20852

Rebekah A. Drezek

Rice University, Department of Bioengineering, Houston, Texas 77251

J. Biomed. Opt. 10(4), 044016 (August 01, 2005). doi:10.1117/1.1989308
History: Received August 03, 2004; Revised March 08, 2005; Accepted March 14, 2005; Published August 01, 2005
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Optimization of device-tissue interface parameters may lead to an improvement in the efficacy of fluorescence spectroscopy for minimally invasive disease detection. Although illumination-collection geometry has been shown to have a strong influence on the spatial origin of detected fluorescence, devices that deliver and/or collect light at oblique incidence are not well understood. Simulations are performed using a Monte Carlo model of light propagation in homogeneous tissue to characterize general trends in the intensity and spatial origin of fluorescence detected by angled geometries. Specifically, the influence of illumination angle, collection angle, and illumination-collection spot separation distance are investigated for low and high attenuation tissue cases. Results indicate that oblique-incidence geometries have the potential to enhance the selective interrogation of superficial or subsurface fluorophores at user-selectable depths up to about 0.5mm. Detected fluorescence intensity is shown to increase significantly with illumination and collection angle. Improved selectivity and signal intensity over normal-incidence geometries result from the overlap of illumination and collection cones within the tissue. Cases involving highly attenuating tissue produce a moderate reduction in the depth of signal origin. While Monte Carlo modeling indicates that oblique-incidence designs can facilitate depth-selective fluorescence spectroscopy, optimization of device performance will require application-specific consideration of optical and biological parameters.

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© 2005 Society of Photo-Optical Instrumentation Engineers

Citation

T. Joshua Pfefer ; Anant Agrawal and Rebekah A. Drezek
"Oblique-incidence illumination and collection for depth-selective fluorescence spectroscopy", J. Biomed. Opt. 10(4), 044016 (August 01, 2005). ; http://dx.doi.org/10.1117/1.1989308


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