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18 August 1997 Optical properties of phantoms and tissue measured in vivo from 0.9 to 1.3 um using spatially resolved diffuse reflectance
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A near infrared spectrometer has been constructed which is capable of performing spatially resolved diffuse reflectance measurements in the wavelength range of 0.9 - 1.6 micrometer. In this technique, broadband light is delivered by an optical fiber to a point on the tissue surface and diffusely reflected light is collected by 300 micrometer fibers located at 15 distances ranging between 1.0 to 10.0 mm from the source. The light from the detector fibers is imaged with a monochromator onto an InGaAs photodiode array. Wavelengths can be selected by automated scanning of the monochromator grating. A diffusion theory model fit to the reflectance versus distance data has been used to estimate the absorption and scattering coefficients ((mu) a and (mu) s') of phantoms and tissue under analysis. Reflectance measurements have been performed on tissue simulating water-based phantoms as well as in vivo on different skin locations. The absorption coefficient of skin was found to have a spectral structure similar to that of water. Unexpected spectral features in the scattering coefficient of skin were observed which may be a result of not considering the layered structure of skin in the current model. The temporal stability of the system has been demonstrated on tissue-simulating phantoms and human volunteers, indicating that the reflectance measurement may be suitable for in vivo monitoring of physiologically induced changes in the absorption and scattering coefficients.
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Jody T. Bruulsema, Joseph E. Hayward, Thomas J. Farrell, Matthias Essenpreis, and Michael S. Patterson "Optical properties of phantoms and tissue measured in vivo from 0.9 to 1.3 um using spatially resolved diffuse reflectance", Proc. SPIE 2979, Optical Tomography and Spectroscopy of Tissue: Theory, Instrumentation, Model, and Human Studies II, (18 August 1997);

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