An intravascular ultrasound imaging system includes a catheter that is insertable into a patient blood vessel. A flushing assembly is in fluid communication with a lumen of the catheter. The flushing assembly flushes air bubbles formed in acoustically-favorable medium in the catheter lumen in response to an event other than a user-initiated flushing prompt. The flushing assembly includes a reservoir containing acoustically-favorable medium for input into the catheter lumen, and a pump coupled to the reservoir. The pump pumps the acoustically-favorable medium from the reservoir to the catheter lumen. A connector is in fluid communication with the reservoir. The connector is coupleable with the catheter lumen. A controller is coupled to the pump. The controller is configured and arranged for controlling operation of the pump.
