1. A method of analyzing a stream of imaging data arranged gridwise in a plurality of picture-elements associated with intensity values pertaining to a level of a detectable tracer in the vasculature of a living subject, the method comprising: for each picture-element, associating a vector of features indicative of temporal intensity variation relative to a baseline intensity, thereby providing a plurality of vectors; clustering the picture-elements according to said vectors, thereby providing a plurality of clusters; and identifying different compartments in the vasculature based on said clusters.