1. A method of automatically detecting vessels in a diagnostic image, said method comprising: accessing digital image data representing a diagnostic image; and detecting vessel candidates in said diagnostic image by processing said digital image data, said step of detecting vessel candidates including identifying edge pixel pairs of vessels in said diagnostic image by iteratively adjusting a plurality of constraints relating to a general direction and shape of a vessel for a next iteration of edge pixel pair identification in said diagnostic image, and determining whether the plurality of said edge pixel pairs form a vessel using features learned from previous data.