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      • The Improved Wavelet Threshold Function and Its Application

        DENG Caixia,CHEN Xiaxia,LI Siqi,XU Yanxin 보안공학연구지원센터 2016 International Journal of Signal Processing, Image Vol.9 No.7

        Images will produce noise in the process of storage and collection. Wavelet threshold de-noising is a simple and effective de-noising method, but the choice of threshold function is a key. The hard-threshold function is discontinuous and there is the deviation between the signal processed by the soft-threshold function and the real signal, so this paper constructs a new threshold function at the origin sufficiently smooth to deal with above problems. A parameter is added to the new threshold function, which is between the soft-threshold and hard-threshold function by adjusting the parameter. The new threshold function can remove the noise effectively, and the image information is well preserved. Hence it plays an important role in follow-up edge detection. The de-noising method with improved wavelet threshold is presented, and then uses morphological edge detection on the new image in this paper. The result shows that the method can detect the complete edge effectively, and the visual effect and objective evaluation are good.

      • An Improved Canny Edge Detection Algorithm

        Yu Chen,Caixia Deng,Xiaxia Chen 보안공학연구지원센터 2015 International Journal of Hybrid Information Techno Vol.8 No.10

        Aimed at the defects of the traditional Canny operator, this paper puts forward an improved algorithm in edge detection. First, this paper gives a new method on selfadaptive image block based on threshold value. Next, by proposing a new hybrid filterbank of self-adaptive median and morphology, we adopt this hybrid filter-bank to smooth the noise image. Then, we add the information of gradient in two bevel directions, so that the information of gradient is more complete. Last, by using the threshold value to process the image of gradient which is after non-maxima suppression, we obtain the image edge. For the noise image, this improved algorithm not only can filter out noise well, but also the image edge is continuous, smooth, clear. The experimental results show that the improved algorithm has a good effect in edge detection, strong capability of noise immunity. The objective evaluation and visual effect are good, too.

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        Role of Myocardial Extracellular Volume Fraction Measured with Magnetic Resonance Imaging in the Prediction of Left Ventricular Functional Outcome after Revascularization of Chronic Total Occlusion of Coronary Arteries

        Yinyin Chen,Xinde Zheng,Hang Jin,Shengming Deng,Daoyuan Ren,Andreas Greiser,Caixia Fu,Hongxiang Gao,Mengsu Zeng 대한영상의학회 2019 Korean Journal of Radiology Vol.20 No.1

        Objective: The purpose of this study was to prospectively investigate the value of the myocardial extracellular volume fraction (ECV) in predicting myocardial functional outcome after revascularization of coronary chronic total occlusion (CTO). Materials and Methods: Thirty patients with CTO underwent cardiovascular magnetic resonance (CMR) before and 6 months after revascularization. Three baseline markers of functional outcome were evaluated in the dysfunctional segments assigned to the CTO vessels: ECV, transmural extent of infarction (TEI), and unenhanced rim thickness (RIM). At the global level, the ECV values of the whole myocardium with and without a hyperenhanced region (global and remote ECV) were respectively measured. Results: In per-segment analysis, ECV was superior to TEI and RIM in predicting functional recovery (area under receiver operating characteristic curve [AUC]: 0.86 vs. 0.75 and 0.73, all p values < 0.010), and it emerged as the only independent predictor of regional functional outcome (odds ratio [OR] = 0.83, 95% confidence interval [CI]: 0.77–0.89; p < 0.001) independent of collateral circulation. In per-patient analysis, global baseline ECV was indicative of ejection fraction (EF) at the follow-up examination (β = -0.61, p < 0.001) and changes in EF (β = -0.57, p = 0.001) in multivariate regression analysis. A patient with global baseline ECV less than 30.0% (AUC, 0.93; sensitivity 94%, specificity 80%) was more likely to demonstrate significant EF improvement (OR: 0.38; 95% CI: 0.17–0.85; p = 0.019). Conclusion: Extracellular volume fraction obtained by CMR may provide incremental value for the prediction of functional recovery both at the segmental and global levels in CTO patients, and may facilitate the identification of patients who can benefit from revascularization.

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