In one embodiment of the present invention, a method of treating a vascular occlusion located at a treatment site within a patient's vasculature comprises positioning an ultrasound catheter at the treatment site. The method further comprises delivering a microbubble therapeutic compound from the ultrasound catheter to the vascular occlusion during a first treatment phase. The method further comprises pausing the delivery of the microbubble therapeutic compound and delivering ultrasonic energy from the ultrasound catheter to the vascular occlusion during a second treatment phase while the delivery of microbubble therapeutic compound remains paused.