Laser-induced autofluorescence of human colonic tissues

The purpose of this study is to perform a preliminary evaluation of the diagnostic potential of laser-induced autofluorescence (LIAF) spectroscopy for colonic rumours 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 far delivering the excitation laser and a fiber bundle for detection of the fluorescence. Using different wavelengths of a CW mixed-gas (Ar/Kr) laser, we 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 520-620nm, 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 625-720nm, 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 I-580/I-630 Or I-580/I-680 can be used to distinguish colonic tumours from normal tissues with good accuracy.