1. An anatomical blood vessel detection and display system, comprising: a user interface enabling a user, via a display of an image presenting anatomical vessels, to, mark a region of interest of a vessel identified by detected boundaries in said image and extend the marked region of interest of said vessel by extending the marking of the detected boundaries in the direction of a point selected by a user on the vessel into a bifurcation via the user interface, by extending a marked vessel boundary in said region of interest by marking a new center point facilitating switching vessel detection from a non-bifurcation to a bifurcation; a detector for automatically detecting a boundary comprising an outline of edges of said vessel in the extended marked region of interest by detecting an edge representing a change in luminance in data representing said image in the extended marked region and in the direction of a point selected by a user in said display image and by tracing the edges by including neighbouring edge pixels having substantially the same direction of edge representative luminance gradient as starting edge pixels; and an image data processor for identifying a minimum vessel diameter in the extended marked region of interest between the detected boundaries and for initiating identification of the location of the minimum vessel diameter in said image.