1. A method for tracking a blood vessel in an image, comprising the steps of: (a) acquiring a fluorescence image of tissue containing a blood vessel; (b) delimiting a segment of the blood vessel with boundaries oriented substantially perpendicular to a longitudinal direction of the blood vessel; (c) constructing at least one curve extending between the delimiting boundaries and located within lateral vessel walls of the blood vessel, wherein the at least one curve terminates at the delimiting boundaries substantially perpendicular to the boundaries; and (d) determining a fluorescence signal intensity in the fluorescence image along the at least one curve, with the signal intensity being representative of vessel perfusion.