A method and an apparatus automatically detect vessels in a diagnostic image. The method according to one embodiment accesses digital image data representing a diagnostic image; detects vessel candidates in the diagnostic image by processing the diagnostic image data, the step of detecting vessel candidates including identifying edge pixel pairs of vessels in a 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 a diagnostic image; and determines whether the plurality of edge pixel pairs form a vessel using learned features.