A system to apply ultrasound energy to a region surrounding blood flow in a blood vessel from a position outside a patient includes: a therapeutic ultrasound transducer comprising a plurality of transducer elements； and a processor configured to control the plurality of transducer elements； wherein the processor is configured to change phase inputs to the transducer elements to move a focus of the transducer at least 1 cm in a first plane which is substantially along a plane of the transducer elements of the therapeutic ultrasound transducer and at least 1 cm in a second plane orthogonal to the first plane； and wherein the processor is further configured to position the focus of the transducer in sequential positions offset from the blood flow in the blood vessel according to a pattern pre-determined by an operator of the system.
