1. A method for mapping vessels comprising: determining a plurality of positions of a coronary guidewire in a plurality of non-contrast enhanced fluoroscopic images; determining, in a plurality of contrast enhanced fluoroscopic images, a plurality of reference points of a vessel segment corresponding to the plurality of positions of the coronary guidewire in a plurality of contrast enhanced fluoroscopic images; and modifying a non-contrast enhanced fluoroscopic image based at least in part on the determined plurality of reference points of a vessel segment.