Study On Laser-induced Fluorescence Spectra Of Nude Mice Models With Human Gastric Cancer

Laser-induced Autofluorescence (LIAF) Spectroscopy has been performed widely in the field of tumor diagnosis recently, for its features, such as real-time, non-side effect and high sensitivity. However, the characteristic peaks of cancer tissues haven't been converged. The research using the technology in this field has mainly contained the following two aspects: the ex vivo tissues'spectral detection and the in vivo detection on the basis of endoscope. Neither of the two methods could provide the real-time spectral information of the peritoneal node during the surgical operation. These disagreement and limitation obstruct the further development of LIAF Spectroscopy.The LIAF system in our lab was set up for collecting the autofluorescence of the tissues, using 405nm laser as the light source. The gastric cancer tissues in the nude mouse models were treated by the biotherapy and tumor areas necrotized in different degrees after the treatment. The variational concentrations of protoporphyrin IX (Pp IX) in these tissues were fully detected. The results shows that with the increasing necrotic areas, the intensities of the characteristic peaks of Pp IX decreases while the counterpart of NADH fails to represent the trend of necrosis. Pp IX would be the sensitive sign for the necrotic degree of gastric cancer and prepare the ground for the application of spectral diagnosis for gastric cancer.The in vivo autofluorescence spectra of the nude mice models were detected during the simulated surgical operation by the LIAF system. The mice in 6 groups, which were labeled with different tumor cell growing times, were the objects for this experiment and the spectra were taken from tissues in their peritoneum and abdominal cavities.The mean spectra of peritoneums in the 6 groups were compared with each other. The intensity of NADH decreased while the one of Pp IX increased with the rise of the tumor cell growing time. It demonstrates that the concentration of NADH is declining while the counterpart of Pp IX is mounting during the cancerous process of tissue. Clustering analysis was used to determine that the cluster number was three and discrimination analysis was performed to calculate the discriminant functions to separate the three clusters. 90.4% of original grouped cases were correctly classified. The misclassification rate of the normal spectra was 33.4%, the one of the abnormal spectra was about 6%. This study provides the information for the further research on the classification of the spectra with discriminant analysis. Principle Component Analysis was performed to extract the information of the spectra taken from the liver, midsection and hypogastrium. The shapes of these three kinds of spectra were different from each other, which the peaks of Pp IX in liver spectrum were much higher than the ones in the other two. The first two components separated the liver spectra from the remaining two ones with 100% accuracy while the third and forth components sorted the spectra of midsection and hypogastrium with 81.82% accuracy. According the differences in the spectra, the LIAF spectroscopy has the potential ability to assist the operation.