| Firstly, the characteristic of laser-induced autofluorescence of human colonic tissue and the advances in using autofluorescence for discriminating colonic cancer have been summarized. Secondly, with four different excitation wavelengths, that is,337,375,405and460nm, the corresponding autofluorescence spectra of freshly excided colonic tissues were measured using a FLS920spectrofluorimeter. Corresponding to each selected excitation wavelengths, fluorescence emission wavelength range were350-650nm,400-650nm,420-650and480-650nm, respectively. The measured autofluorescence spectral were processed using principle component analysis (PCA) combined with linear discriminant analysis (LDA) method. Under337and460nm wavelength excitation, autofluorescence spectra of colon normal tissues are significantly different with those of cancerous tissues. Satisfied diagnostic specificity (89.5%) but low sensitivity (73.5%) was obtained on processing spectral data of337nm excitation. At the excitation wavelength of460nm, the higher diagnostic sensitivity, specificity and accuracy rate (85.3%,86.8%and86.1%) were obtained. The results show that the optimum excitation wavelengths of the ex vivo diagnosis of colon cancer are337and460nm. PCA combining with LDA are the effective algorithm for discriminating of colon normal and cancerous tissue. Thirdly, a portable autofluorescence spectrum system was developed for diagnosing of colonic tissue based on the results from discriminant analysis. Compared with the obtained spectra trom FLS920, the performance of the portable autofluorescence spectrum system was evaluated. Finally, the main accomplished results were summarized and the potential work was briefly mentioned. |
