Published 16 January 2012 Stroke and heart attack, which could be led by a kind of cerebrovascular and cardiovascular disease named as atherosclerosis, would seriously cause human morbidity and mortality. It is important for the early stage diagnosis and monitoring medical intervention of the atherosclerosis. Carotid stenosis is a classical atherosclerotic lesion with vessel wall narrowing down and accumulating plaques burden. The carotid artery of intima-media thickness (IMT) is a key indicator to the disease. With the development of computer assisted diagnosis technology, the imaging techniques, segmentation algorithms, measurement methods, and evaluation tools have made considerable progress. Ultrasound imaging, being real-time, economic, reliable, and safe, now seems to become a standard in vascular assessment methodology especially for the measurement of IMT. This review firstly attempts to discuss the clinical relevance of measurements in clinical practice at first, and then followed by the challenges that one has to face when approaching the segmentation of ultrasound images. Secondly, the commonly used methods for the IMT segmentation and measurement are presented. Thirdly, discussion and evaluation of different segmentation techniques are performed. An overview of summary and future perspectives is given finally.

针对超音速飞行器在大气中飞行时所产生的湍流脉动气动光学效应进行了理论分析与计算,并对气动模糊图像进行了复原。首先根据计算流场时使用的湍流模型及其控制方程,计算脉动流场气动光学效应所对应的点扩散函数。计算结果表明,气动光学点扩散函数的幅度响应函数具有低通特征,使目标图像成像模糊。在相同飞行高度下,马赫数越高,图像模糊越严重。通过把气动光学效应传递函数应用于风洞实验吹风前图像,并将得到的气动模糊图像与吹风后实测图像的对比,验证了理论点扩展函数的正确性。最后,提出了一种改进的Landweber迭代图像复原方法对气动光学效应进行了校正。该方法在每一步迭代时对松弛因子进行修正,具有较快收敛速度和更好的复原效果。

A noise erosion operator based on partial differential equation (PDE) is introduced, which has an excellent ability of noise removal and edge preservation for two-dimensional (2D) gradient data. The operator is applied to estimate a new diffusion coefficient. Experimental results demonstrate that anisotropic diffusion based on this new erosion operator can efficiently reduce noise and sharpen object boundaries.