The invention generally relates to intravascular imaging and methods of improved image quality by triggering image operations with a vessel flush. The invention provides systems and methods for intravascular imaging in which a flush such as the influx of clear saline or radiopaque dye triggers the imaging operation. The flush is detected by a mechanism&mdashsuch as a pressure sensor or optical device on the imaging catheter, an external angiography system, or other device&mdashthat uses detection as a trigger to initiate imaging. Thus, when the blood is flushed, the catheter automatically takes a picture of the vessel wall.
