Process of Change from Ultrasonic Wave to Shock Wave in Extracorporeal Shock Wave Lithotripsy Using Piezoceramic Transducer

The process of change from ultrasonic wave to shock wave by non-linear effect in a shock wave lithotripter using a piezoceramic transducer was observed by a membrane-type PVDF hydrophone. The peak sound pressure at the focussing point is 1.6 MPa at a 60 V driving voltage. As there is no shock front, this wave cannot disintegrate a stone. At 3.5 kV, a detected waveform which has a shock front is different from that of 60 V and is able to disintegrate a stone. The peak pressure of this shock wave is 110 MPa. The focal zones of ultrasonic and shock waves are 3 mm×19 mm and 1 mm×20 mm, respectively.