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Background: Gastric cancer is one of the most common malignancies that pose a serious risk to human health worldwide. Lymph node metastasis may serve as an important prognostic factor for gastric cancer. However, the use of lymph nodes as a prognostic indicator for gastric cancer may lead to stage migration. The aim of this study is to establish a nomogram model to increase the prognostic accuracy of gastric cancer by validating the prognostic role of lymph node metastatic risk. Methods: A total of 3716 patients with gastric cancer were included in this study based on information from the SEER database. The risk factors for lymph node metastasis were analyzed correlatively. Prognostic factors were analyzed by COX regression, on which nomograms were constructed. The model was validated with ROC and C-indices, and Kaplan-Meier curves were evaluated and analyzed for each prognostic factor. Results: Age, sex, T-stage, N-stage, M-stage, tumor size and lymph node ratios all served as independent prognostic factors for gastric cancer. lymph node metastasis ratio is a prognostic factor in gastric cancer that is superior to lymph node number. The nomogram model has 3- and 5-year AUC values of 0.797 and 0.817 respectively, with a C-index of 0.730. Conclusion: As a prognostic factor of gastric cancer, lymph node metastasis ratio can reduce stage migration, and its inclusion in the nomogram model is superior to the TNM staging system to evaluate the prognosis of gastric cancer. The nomogram model we have developed has high reliability and accuracy and thus can inform personalized clinical treatment for gastric cancer patients.

This thesis describes a hand-held confocal optical scanner for cellular imaging. In current clinical practice, the detection of disease like colorectal cancer is performed using endoscopy and biopsy. Random biopsies and oversampling are usually required to reduce false results, so potentials exist for non-invasive optical diagnostic techniques. Optical microscopy techniques such as confocal laser scanning microscopy provide images for biological tissues at a micrometer level. The challenge is to miniaturize the system into a form of hand-held devices or catheters. The developed system in this thesis consists of a portable scanner probe and a reflectance confocal imaging unit. The imaging unit was constructed in an all-fiber configuration for convenient packaging. Confocal scanning was performed at 785 nm laser illumination with a piezoelectric fiber scanner probe. The fiber-based probe was constructed by mounting a fiber directly on a two-dimensional piezoelectric bender. Horizontal image scanning has been successfully achieved, and the developed device can provide image resolution of 1.16-1.41 μm in the lateral direction and can resolve cell structures. The operating scanning speed is 1.25 frames per second with 88 × 88 μm² field of view, potentially applicable to real-time imaging. Image results were presented with onion epidermis and optical paper samples in comparison to galvanometer mirrors based confocal laser scanning unit.