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; a detector for automatically detecting a boundary of said vessel in the extended marked region of interest by detecting an edge representing a change in luminance in data representing said image; 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.