Multiexcitation fluorescence and reflectance spectroscopy as a real time guide to biopsy in vivo

A compact excitation-emission spectrofluorimeter system used to acquire tissue fluorescence and reflectance with fiber optic light delivery and collection is presented. Ten dye cells are pumped by a XeCl excimer laser, creating laser excitation from 308 nm to 505 nm, which is used to excite tissue fluorescence. A xenon-flash lamp is employed to obtain the reflectance spectrum of the corresponding tissue spot. Eleven fluorescence spectra and one white light diffuse reflectance spectrum are collected in vivo in 0.2 seconds and can be potentially analyzed in real time to obtain diagnostic information. The instrument can be used for early cancer detection. The measured fluorescence and reflectance spectra are used to model the intrinsic fluorescence of the tissue, which gives important insight into its biochemical composition (tryptophan, collagen, elastin, NADH, etc.) and metabolic state. Diffuse reflectance provides information about tissue morphology, in terms of the scattering and absorption coefficient. By subtracting the diffusely reflected component from the measured reflectance, light scattering spectroscopic (LSS) information due to single backscattering from epithelial cell nuclei can be obtained. LSS provides information about the size distribution of cell nuclei. The parameters give diagnostic information, which can be used to guide the physician in real time while taking biopsies of invisible tissue abnormalities.