1. A method for use with an image of blood vessels of a subject, comprising: using at least one processor: in response to a user designating a single point on the image: automatically identifying a target portion of a blood vessel in a vicinity of the designated point; performing quantitative vessel analysis on the target portion of the blood vessel; and generating an output based upon the quantitative vessel analysis, wherein identifying the target portion comprises designating a longitudinal portion of the blood vessel having a proximal end that is at a first distance from the point in a proximal direction, and having a distal end that is at a second distance from the point in a distal direction.