Systems and methods deliver ultrasound energy to an ultrasound transducer having an impedance subject to variations. The systems and methods electrically couple an ultrasound generator to the ultrasound transducer to deliver ultrasound energy. The systems and methods deliver ultrasound energy to the...http://www.google.se/patents/US7335169?utm_source=gb-gplus-sharePatent US7335169 - Systems and methods for delivering ultrasound energy at an output power level that remains essentially constant despite variations in transducer impedance
