Study of laser autofluorescence of human colon tissues

The purpose of this study is to perform a preliminary evaluation of the diagnostic potential of laser-induced autofluorescence (LIAF) spectroscopy for colon tumours using fluorescence intensity ratios at specific wavelengths. Measurements were made on normal mucosa and adenocarcinoma of human colon tissues. Each tissue section was examined using an optical probe consisting of a central fiber for delivering the excitation laser and a fiber bundle for detection of the fluorescence. Using different wavelengths of a CW mixed-gas (Ar/Kr) laser, the authors measured and analyzed the LIAF spectra of tissues through a polychromator coupled with a CCD detector. It can be found that in the range of 520-620 nm, the spectral shapes of tumour tissues are very similar to the normal tissue spectra, and the autofluorescence intensities of normal tissues are about threefold higher than those of tumour tissues. However, in the range of 625-720 nm, the autofluorescence intensities of tumour tissues are higher than those of normal tissues. The spectral characteristic peaks (around 635, 675 and 703 nm) arising from endogenous porphyrins can be observed in some tumour tissues. The preliminary results show that the autofluorescence intensity ratio of I₅₈₀/I₆₃₀ Of. I₅₈₀/I ₆₈₀ can be used to distinguish colonic tumours from normal tissues with good accuracy