A fast spectroscopic system for superficial and local determination of the absorption and scattering properties of tissue (480 to 950 nm) is described. The probe can be used in the working channel of an endoscope. The scattering properties include the reduced scattering coefficient and a parameter of the phase function called gamma, which depends on its first two moments. The inverse problem algorithm is based on the fit of absolute reflectance measurements to cubic B-spline functions derived from the interpolation of a set of Monte Carlo simulations. The algorithm's robustness was tested with simulations altered with various amounts of noise. The method was also assessed on tissue phantoms of known optical properties. Finally, clinical measurements performed endoscopically in vivo in the stomach of human subjects are presented. The absorption and scattering properties were found to be significantly different in the antrum and in the fundus and are correlated with histopathologic observations. The method and the instrument show promise for noninvasive tissue diagnostics of various epithelia.
An optical tissue diagnosis technique, often called "optical biopsy", has been developed, It is based on the simultaneous determination of the optical properties of tissues such as the reduced scattering coefficient µ s ' and the absorption coefficient µ a . These data are obtained by applying a small diameter probe (ø 2mm) on tissues, through the working channel of usual endoscopes. The simultaneous determination of µ a and µ s ' with a local probe was made possible by the consideration of the first two moments of the phase function and a proven model of light propagation in tissues at propagation length comparable to the scattering mean free path. Non-invasive measurements of the optical coefficients of superficial tissues have been obtained in vivo at different wavelength
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