Study of shapes and motions of coronary arteries determined by analysis of intravascular ultrasound

We describe methods to extract, measure and visualize three-dimensional shapes from Intracoronary Vascular Ultrasound (IVUS) videos recorded in vivo, with image segmentation for lumen and intima thickening, and functional model recovery from discrete representations, with IVUS video segmentation, probe motion recovery, and verification and applications of all the methods.; We have developed a novel time-variant shape extraction method that is based on the principle of IVUS video formation and heart vessel phasic motion. We have demonstrated that image distance, computed by a multiresolution approach, is an efficient and reliable way to recover phase information directly from cardiac IVUS image sequences. The shape reconstruction is fully automatic and takes linear time with respect to the number of frames. This robust approach has been successfully applied to modest-image-quality digitized videos. The recovered shapes not only show strong visual coherence but also detailed phasic changes of important anatomical and physiological structures. The recovered three-dimensional model is properly aligned by three-dimensional registration techniques.; Some biomechanical studies require a smooth model. For this, we have introduced a new functional model recovery method that computes an implicit polynomial representation from any discrete point-set input. This new minimal description length based model is both stable and repeatable. We have also developed a shortest-path segmentation algorithm that is based on line-integral edge weighting. We have shown that this algorithm performs well for extracting a global optimal path for a curved area of interest from speckle images. We apply the algorithm to IVUS videos to analyze the time-dependency of the morphological characteristics of epicardial arteries. We guide the video segmentation process with an automatically-computed segmentation graph. Using this, we have achieved significant performance gain over traditional video segmentation algorithms, and obtaining vessel lumen contours that match well with those traced by an expert.; This system has been applied to animal studies, to visualize and measure intima thickness and lumen areas in response to acute mean arterial pressure changes, and to track changes of vessel size and intima thickening for a period spanning over 15 months.