There is provided in accordance with an exemplary embodiment of the invention a method and for keeping an ultrasound emission element away from a wall of a blood vessel or cavity comprising: inserting a catheter comprising the ultrasound emission element into a blood vessel or body cavity such that the ultrasound emission element is prevented from contacting a wall of the blood vessel or the cavity. There is also provided in accordance with an exemplary embodiment of the invention a device for keeping an ultrasound emission element away from a wall of a blood vessel or lumen.
