In vivo autofluorescence spectroscopy of human bronchial tissue to optimize the detection and imaging of early cancers

We are developing an imaging system to detect pre-/early cancers in the tra cheo-bronchial tree. Autofluorescence might be useful but many features rem ain suboptimal. We have studied the autofluorescence of human healthy, meta plastic and dysplastic/CIS bronchial tissue, covering excitation wavelength s from 350 to 480 nm. These measurements are performed with a spectrofluoro meter whose distal end is designed to simulate the spectroscopic response o f an imaging system using routine bronchoscopes. Our data provide informati on about the excitation and emission spectral ranges to be used in a dual r ange detection imaging system to maximize the tumor vs healthy and the tumo r vs inflammatory/metaplastic contrast in detecting pre-/early malignant le sions. We find that the excitation wavelengths yielding the highest contras ts are between 400 and 480 nm with a peak at 405 nm. We also find that the shape of the spectra of healthy tissue is similar to that of its inflammato ry/metaplastic counterpart. Finally we find that, when the spectra are norm alized, the region of divergence between the tumor and the nontumor spectra is consistently between 600 and 800 nm and that the transition wavelength between the two spectral regions is around 590 nm for all the spectra regar dless of the excitation wavelength, thus suggesting that there might be one absorber or one fluorophore. The use of backscattered red light enhances t he autofluorescence contrast. (C) 2001 society of Photo-Optical Instrumenta tion Engineers.