Absolute autofluorescence spectra of human healthy, metaplastic, and earlycancerous bronchial tissue in vivo

Autofluorescence is emerging as a useful tool for the detection of early ca ncers in the bronchi. It has already produced interesting results, which ha ve been implemented in commercial imaging devices. Their design relies on t he spectroscopy of the tissues of interest. However, a large majority of th ese autofluorescence spectroscopy studies have been presented in arbitrary units. This is a drawback for, in particular, the designing of imaging devi ces based on autofluorescence, Using correction factors and a spectral sens itivity correction curve, we determined the absolute spectral distribution of the tissue autofluorescence in vivo. These measurements were performed o n healthy, metaplastic, and dysplastic bronchial tissues at several excitat ion wavelengths ranging from 350 to 495 nm. Moreover, we measured at a fixe d distance between the tissue and the probe to avoid geometric distortions of the spectra that are due to the optical characteristics of tissue. We fo und that the order of magnitude of the autofluorescence brightness was stab le as the excitation wavelengths varied (on the order of 5 pW/muW x nm at t he maximum of the fluorescence emission spectra). (C) 2001 Optical Society of America.