Delineating vessels in an angiogram involves two methods: graph generation and skeletonization. Generating a graph includes obtaining a digital image of an angiogram, recognizing a first growth point within the image, and identifying region boundary points around the growth point. The region boundary points are connected to the first growth point, thereby creating edges of a graph. The boundary point that has the greatest intensity is then selected as a second growth point, and additional region boundary points around the second growth point are identified. The additional region growth points are connected to the second growth point. The region boundary point with the greatest intensity in the image is then selected as a third growth point, and the method repeats until each point in the image is connected to another point in the graph. The skeletonization of the graph begins with recognizing a point in the graph as an endpoint of a vessel. This may be done explicitly through manual or automatic selection of specific points. It may also be done implicitly through a trimming process whereby graph branches of fewer than a certain number of connected points are discarded. The endpoints in the remaining branches are recognized as vessel endpoints. The skeletonization concludes with display of the delineated vessels. This may be done by superimposing the vessels in two or three dimensions over a conventional two-dimensional angiographic image such as a maximum intensity projection (MIP).