CT 질감특징분석을 이용한 인간 상피세포 성장인자 수용체 2 (HER2) 양성 진행성 위암의 종양이질성 평가: trastuzumab 치료 후 생존율과의 연관성 평가

학위논문 (석사)-- 서울대학교 대학원 : 임상의과학과, 2017. 2. 김영훈.Introduction Image texture analysis is a noninvasive technique for quantifying intratumoral heterogeneity, with derived texture features reported to be closely related to the treatment outcome of tumors. Gastric cancer is one of the most common tumors and the third leading cause of cancer-related deaths worldwide. Although trastuzumab is associated with a survival gain among patients with human epidermal growth factor receptor 2 (HER2)-positive advanced gastric cancer, optimal patient selection is challenging. The purpose of this study was to determine whether CT texture features of HER2-positive gastric cancer were related to the survival rate after trastuzumab treatment. Patients and methods Patients diagnosed with HER2-positive advanced gastric cancer from February 2007 to August 2014 were retrospectively selected. Using in-house built software, histogram features (kurtosis and skewness) and gray-level co-occurrence matrices (GLCM) features (angular second moment [ASM], contrast, entropy, variance, and correlation) were derived from the CT images of HER2-positive advanced gastric cancer in 26 patients. All the patients were followed up for more than 6 months, with no confirmed deaths. The patients were dichotomized into a good and poor survival group based on cutoff points of overall survival of 12 months. A receiver-operating characteristics (ROC) analysis was performed to test the ability of each texture parameter to identify the good survival group. Kaplan–Meier curves for patients above and below each threshold were constructed. Results Using a threshold of >265.8480 for contrast, >488.3150 for variance, and ≤0.1319×10-3. for correlation, all of the area under the ROC curves showed fair accuracy (>0.7). Kaplan–Meier analysis showed statistically significant survival difference between two groups according to optimal cutoff values of contrast, variance, correlation and ASM. Conclusion Heterogeneous texture features on CT images were associated with better survival in patients with HER2-positive advanced gastric cancer who received trastuzumab-based treatment. Therefore, texture analysis shows potential to be a clinically useful imaging biomarker providing additional prognostic information for patient selection.1. Introduction 1 2. Patients and methods 2 2.1 Patients 2 2.2 CT examination 3 2.3 Texture analysis 3 2.4 Statistical analysis 4 3. Results 5 3.1 Patients 5 3.2 Survival analysis 6 4. Discussion 9 References 13 요약(국문초록) 17Maste

The effects of Thomson scattering and chemical mixing on early-time light curves of double peaked type IIb supernovae

Previous numerical simulations of double-peaked SNe IIb light curves have demonstrated that the radius and mass of the hydrogen-rich envelope of the progenitor star can significantly influence the brightness and timescale of the early-time light curve around the first peak. In this study, we investigate how Thomson scattering and chemical mixing in the SN ejecta affect the optical light curves during the early stages of the SNe IIb using radiation hydrodynamics simulations. By comparing the results from two different numerical codes (i.e., \stella{} and \snec{}), we find that the optical brightness of the first peak can be reduced by more than a factor of 3 due to the effect of Thomson scattering that causes the thermalization depth to be located below the Rosseland-mean photosphere, compared to the corresponding case where this effect is ignored. We also observe a short-lived plateau-like feature lasting for a few days in the early-time optical light curves of our models, in contrast to typical observed SNe IIb that show a quasi-linear decrease in optical magnitudes after the first peak. A significant degree of chemical mixing between the hydrogen-rich envelope and the helium core in SN ejecta is required to reconcile this discrepancy between the model prediction and observation. Meanwhile, to properly reproduce the first peak, a significant mixing of \nifs{} into the hydrogen-rich outermost layers should be restricted. Our findings indicate that inferring the SN IIb progenitor structure from a simplified approach that ignores these two factors may introduce substantial uncertainty.Comment: 28 pages, 21 figures, accepted for Ap

Taxonomy and Evaluations of Low-Power Listening Protocols for Machine-to-Machine Networks

Even though a lot of research has made significant contributions to advances in sensor networks, sensor network protocols, which have different characteristics according to the target application, might confuse machine-to-machine (M2M) network designers when they choose the protocol most suitable for their specific applications. Therefore, this paper provides a well-defined taxonomy of low-power listening protocols by examining in detail the existing low-power sensor network protocols and evaluation results. It will also be very useful for helping M2M designers understand specific features of low-power media access control protocols as they design new M2M networks