In one embodiment of the present invention, a method of applying ultrasonic energy to a treatment site within a patient's vasculature comprises positioning an ultrasound radiating member at a treatment site within a patient's vasculature. The method further comprises activating the ultrasound radiating member to produce pulses of ultrasonic energy at a cycle period T≦1 second. The acoustic parameters such as peak power, pulse width, pulse repetition frequency and frequency or any combination of them can be varied non-linearly.