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15 April 2005 Feasibility of extracting tissue optical properties from amplitude OCT data during optical skin clearing
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This paper investigates three different techniques to investigate the dynamic change of the attenuation coefficient in in-vitro hamster skin during optical skin clearing using a hyper-osmotic solution of 50% glycerol. The tissue is imaged using an amplitude based OCT system with a wavelength of 1290 nm during the clearing experiment. The tissue sample rested on a mirror surface and OCT images of the tissue and mirror were acquired in 1 minute intervals over a 45 minute period. Intensity profiles were obtained from averaging A-scans at each time interval. The tissue optical properties were determined by curve fitting an exponential function to the acquired intensity profiles, by linear line fit between front- and mirror surface reflection as well as by fitting the photo detector voltage at front- and mirror surface peaks to a modified expression of Beer's Law. In addition, another experimental set-up was used to evaluate focus effects on the back scattered signal from the mirror underneath an in-vitro porcine skin sample which was dehydrated in air to mimic optically cleared tissue. Both, tissue and mirror were mounted onto two independent micro translation stages in order to determine focal effects on the mirror signal. Results show that exponential curve fitting initially yields acceptable data for the attenuation coefficient but later introduces significant error due to the altered light propagation through the tissue due to the applied clearing agent. Attempting to use a linear fit between front- and mirror reflections does not yield physically meaningful data while using the detector voltage read-out in combination with Beer's law yields acceptable results comparable with tissue data published in the literature. Focal effects account for 1.5 to 2.5 dB higher signals than otherwise can be expected from the back reflection of the mirror underneath a scattering tissue sample if the mirror is in the focal plane of the input optics.
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Oliver Stumpp, A.J. Welch, and Thomas E. Milner "Feasibility of extracting tissue optical properties from amplitude OCT data during optical skin clearing", Proc. SPIE 5695, Optical Interactions with Tissue and Cells XVI, (15 April 2005);

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