According to some embodiments there is provided a method for controlling a treatment effect on blood vessel tissue during an ultrasonic treatment, the method comprising positioning an ultrasonic transducer device in the blood vessel lumen； controlling a treatment effect by controlling fluid flow, wherein controlling comprises deploying a fluid restrictor at a location relative to the transducer effective to block at least a portion of fluid flowing upstream, downstream or adjacent the transducer. According to some embodiments there is provided an ultrasonic transducer device sized for placement in a body lumen, and comprising a fluid restrictor effective to block at least a portion of fluid flowing upstream, downstream or adjacent the transducer. In some embodiments, the fluid is blood.本発明によれば、超音波エネルギを放出するように適応された素子と、前記素子の少なくとも一部の体積に電圧を印加するように構成された少なくとも２つの電極と、血液中に存在するときにガス気泡を保持するように適応されたガス気泡閉じ込め領域とを備えた、体内医療用の超音波カテーテルが提供される。【選択図】図５Ａ－５Ｄ
