The present invention provides low profile intravascular ultrasound catheters adapted to access sites within the patient's body through narrow blood vessels, e.g., the radial artery. In an embodiment, a low profile catheter comprises an catheter sheath, a short guidewire receiver attached to the distal end of the catheter sheath, and a telescope assembly at the proximal end. The catheter sheath comprises a main portion and a tapered portion for increased flexibility toward the distal end of the catheter. In one embodiment, a rotatable and translatable imaging core is received within the catheter sheath for ultrasound imaging. A short guidewire receiver is used to allow the imaging core to be advanced farther distally with respect to the distal end of the catheter. In an embodiment, the catheter sheath extends through a portion of the telescope assembly to provide enhanced support of the imaging core within the telescope assembly.