LASER-INDUCED FLUORESCENCE SPECTROSCOPY AT ENDOSCOPY - TISSUE OPTICS,MONTE-CARLO MODELING, AND IN-VIVO MEASUREMENTS

The optical properties (absorption coefficient, scattering coefficient and the anisotropic factor of scattering) and fluorescence characteri stics of normal and abnormal bronchial tissue were measured in vitro. After adding additional blood optical properties to in vitro optical p roperties of tissue, the in vivo bronchial fluorescence was simulated and analyzed by Monte Carlo modeling. The Monte Carte simulation resul ts showed that with an appropriate illumination and fluorescence colle ction geometry, the distortion of in vivo fluorescence spectra of tiss ue caused by variations of optical properties at different wavelengths could be much reduced. Based on these results, a spectrofluorometry s ystem was developed for the collection of in vivo laser-induced fluore scence spectra of tissue during endoscopy. In comparing the in vivo fl uorescence spectral shape of bronchial tissue collected by this system with the intrinsic one obtained in vitro, we found no obvious distort ion in the in vivo spectra. This was completely consistent with the an alysis of Monte Carlo modeling. The in vivo measurement results demons trated that significant differences in fluorescence intensity between normal and diseased bronchial tissue (dysplasia, carcinoma in situ) ca n be used to differentiate them from each other. Also, changes in fluo rescence intensity are more robust for detecting abnormal tissues than the differences in spectral characteristics.