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In order to overcome drawbacks in manual identification of vulnerable atherosclerotic plaques,a method for automatic identification of vulnerable plaques is proposed based on computerized analysis of intravascular ultrasound images.First,the Contourlet transform is combined with the Snake model to segment images and detect lumen borders and external elastic membranes.Two categories of new features representing texture and elasticity of plaques are then automatically extracted to quantitate the features of plaques.The texture features consist of first-order statistics and features from the gray-level coocurrence matrix,and the elastic features are extracted from strain tensors estimated by nonrigid image registration.Finally,three types of features are used to design classifiers including Fisher linear discrimination,support vector machines,and generalized relevance learning vector quantization.The experimental results on 124 plaques,consisting of 36 vulnerable and 88 nonvulnerable ones,reveals that 20 morphological features,24 texture features and 6 elastic features has significant difference(P0.05) between the two types of plaques.The Support Vector Machine(SVM) outperformes the other two classifiers with the sensitivity,specificity,correct rate,and Youden's index of 91.7%,97.7%,96.7%,and 89.4%,respectively.Therefore,the proposed method can automatically and accurately identify vulnerable plaques.

A high-resolution loess section in the western Chinese Loess Plateau, Yuanbao Section, was sampled for organic carbon isotopic analyses. The soil organic carbon isotope (δ 13Corg) varied between −22.6‰ and −27.5‰ during the last glacial at the section. During the last interstadial, the δ 13Corg values were more negative than those in both early and late periods of the last glacial by 4‰ The isotopic composition indicates a coupled response of the pure C3 plants to the temperature, precipitation and the concentration of atmospheric CO2. Decrease in temperature and the atmospheric CO2 concentration from the last interstadial to Last Glaicial Maximum (LGM) caused the organic carbon isotopes to become positive by 1.5‰–2.0‰ The amplitude of 4‰ in the δ 13Corg variation during the last glacial should be mainly caused by the precipitation change. Therefore, the δ 13Corg variations of the Yuanbao Section during the last glacial period documented the large-amplitude fluctuation of the monsoon precipitation, which is estimated to be 250–310 mm more during the last interstadial than that in the LGM, and 100 mm more than that during early last glacial. The rapid changes of the monsoon precipitation on millennial scale during the last glacial have also been recorded in the isotopic variations in Yuanbao loess section. As the isotopic composition varies complicatedly as shown in the loess-paleosol sequence, it cannot be simply attributed to the abundances of C3 and C4 plants or be used as an indicator of the summer monsoon variations.