A method and apparatus for endoscopic removal of compliant biological tissues utilizing an endoscopic ultrasonic aspirator comprising irrigation and aspiration means, a piezoelectric ultrasonic transducer, a first resonator such as a half-wave stepped velocity transformer, a probe including a second...http://www.google.de/patents/US4922902?utm_source=gb-gplus-sharePatent US4922902 - Method for removing cellular material with endoscopic ultrasonic aspirator
