A catheter assembly for an intravascular ultrasound system includes a hub disposed at a proximal end of a catheter. The hub includes a rotatable connector shaft disposed at least partially in a lumen that extends from the hub to a distal end of the catheter. A pumping apparatus is coupled to the connector shaft such that rotation of the connector shaft causes a corresponding rotation of the pumping apparatus. A reservoir is in fluid communication with the pumping apparatus. The reservoir is configured and arranged for inputting an acoustically-favorable medium to the pumping apparatus. An imaging core is configured and arranged for inserting into the lumen. The imaging core includes an imaging device coupled to a rotatable drive member. The rotatable connector shaft is coupled to a proximal end of the drive member such that rotation of the connector shaft causes a corresponding rotation of the imaging core.