Automatic indexing of cine-angiograms

Abstract

A method and system for identifying end systole and end diastole frames within an angiography sequence. A plurality of images produced during an angiography sequence are digitized, producing digital image data in which gray scale values for each of the pixels in the images are represented. The digital image data are input to a computer (48) to determine the frames in which the coronary arteries are most visible. The coronary arteries are made visible in the images by injecting a radio-opaque contrast substance into the arteries. The frames that occur a end diastole are preferred for diagnostic analysis because the arteries are distended, spread apart from each other, and moving very slowly. To identify such frames for further analysis, the total length of edges within a centered window covering approximately one-fourth of each image is determined. The edges represent spatial transitions between relatively light and dark areas in the image that occur across the borders of the coronary arteries. At end diastole during the cardiac cycle, the total length of the coronary arteries within the window is substantially less than at end systole, when the heart has contracted to a minimum volume. Frames in which a local maximum total edge length is observed thus depict the arteries at end systole. Similarly, frames having a local minimum total edge length show the arteries at end diastole. Either a spatial method or a discrete cosine transform (DCT) method is used for determining the total edge length in each frame.