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Title: Near-Infrared Autofluorescence Imaging and Spectroscopy for Early Detection of Precancer and Cancer in the Colon
Keywords: Near-infrared, Autofluorescence, Diffuse reflectance, Polarization, PCA-LDA, Colon cancer
Issue Date: 29-Jul-2011
Citation: SHAO XIAOZHUO (2011-07-29). Near-Infrared Autofluorescence Imaging and Spectroscopy for Early Detection of Precancer and Cancer in the Colon. ScholarBank@NUS Repository.
Abstract: This dissertation presents the investigation on the diagnostic utility of NIR AF imaging and spectroscopy to detect precancer and cancer in the colon. We have developed a novel integrated NIR AF and NIR diffuse reflectance (DR) imaging technique for colon cancer detection. 48 paired colonic tissue specimens were tested to evaluate the diagnostic feasibility of NIR AF imaging for differentiating cancer from normal tissues. The results suggest that the colon cancer tissues can be well separated from normal colonic tissues. The polarization technique was also coupled into the integrated NIR AF imaging system to further improve the diagnostic accuracy for colon cancer demarcation. The ratio imaging of NIR DR to NIR AF with polarization conditions achieved the best diagnostic accuracy, affirming the potential of the integrated NIR AF/DR imaging with polarization for improving the early detection and diagnosis of malignant lesions in the colon. We have also developed an endoscope-based NIR AF spectroscopy technique to realize real-time in vivo NIR AF spectra measurements from colonic tissue during clinical colonoscopic examination. Under the guidance of conventional wide-field endoscopic imaging, a novel bifurcated flexible fiber-probe has been developed and integrated into the NIR AF spectroscopy system to measure in vivo NIR AF spectra from different types of colonic tissues from 100 patients. Multivariate statistical techniques (PCA-LDA) are employed for developing effective diagnostic algorithms for classification of different colonic tissue types. The diagnostic algorithms yield overall accuracies of 88.9%, 85.4% and 91.4% respectively, for classification of colonic normal, hyperplastic, and adenomatous polyps. This indicates that NIR AF spectroscopy is a unique diagnostic means for in vivo diagnosis and characterization of precancerous and cancerous colonic tissues. To further investigate the origins of tissue biochemicals responsible for the differences of NIR AF among different types of colonic tissues, we have constructed a non-negativity-constrained least squares minimization (NNCLSM) biochemical model to estimate the biochemical compositions of colonic tissues. The NIR AF spectra from the nine representative biochemicals (i.e., collagen I, elastin, ?-NADH, FAD, L-tryptophan, hematoporphyrin, 4-pyridoxic acid, pyridoxal 5?-phosphate, and water) were found the most significant in colonic tissue for optimally fitting the measured in vivo NIR AF spectra colonic tissue. We also compared the fitting results between in vivo and ex vivo datasets. NIR AF spectroscopy provides new insights into biochemical changes of colonic tissue associated with cell proliferation and metabolic rate during the cancer progression. Moreover, we have also investigated the diagnostic ability of the integrated visible (VIS) and NIR DR spectroscopy technique for detection and diagnosis of colon cancer. High-quality integrated VIS-NIR DR spectra (400-1000 nm) from normal and cancer colonic mucosal tissue were acquired and significant differences are observed in DR spectra between normal (n=58) and cancer (n=48) colonic tissue, particularly in the spectral bands near 420, 540, 580 and 1000 nm. Best differentiation between normal and cancer tissues can be achieved using the integrated VIS-NIR DR spectroscopy as compared to VIS or NIR DR spectroscopy alone, indicating the potential of the integrated VIS-NIR DR together with PCA-LDA algorithms for improving early diagnosis of colon cancer. The results of this dissertation establishe a proof of principle that NIR AF/DR imaging and spectroscopy techniques have the potential to be a clinically useful tool to complement the conventional white light endoscopy for non-invasive in vivo diagnosis and detection of colonic precancer and cancer during clinical colonoscopic screening.
Appears in Collections:Ph.D Theses (Open)

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