An apparatus and method for using ultrasound augmented with microbubbles,thrombolytic drugs or other agents for clot lysis wherein at least oneultrasound transducer (20) generates a plurality of acoustic signals and time,amplitude, phase and frequency modulation of the signals to provide moreuniform power delivery with fewer gaps in the ultrasound field. Interferencepatterns from one or multiple transducers (12, 13, 14, 16, 20) are constantlyshifted in position. A phased array (30) of transducers (31) may generate adirected beam that is swept over an area or directed to a specific location.In another embodiment, an array of transducers (12, 13, 14, 16, 20, 30) maygenerate ultrasound at a number of slightly varying frequencies to produce aninterference pattern that sweeps in and out through the targeted tissue. Asingle array may be used to produce both effects simultaneously or separately.
