Dual pulse shock wave lithotripsy: in vitro and in vivo study

PURPOSE: We evaluated the performance of a novel dual pulse lithotriptor for extracorporeal lithotripsy. MATERIALS AND METHODS: A piezoelectric lithotriptor was modified to produce pairs of successive (tandem) shock waves. Four kidney stone models were exposed in vitro to 500 single shock waves with a standard lithotriptor. Another set of stones was exposed 1 at a time to 250 pairs of shock waves with the tandem lithotriptor. The time delay between the first and second shock waves was increased in steps of 50 microseconds between 100 and 600 microseconds. Four stones were used per delay, ie 44 phantoms were fractured with the tandem system. Rabbits were used in vivo to demonstrate that the novel device does not produce more tissue trauma. Five rabbits were exposed to shock waves generated by the new device, 5 were treated with the standard system and 5 served as the sham treated group. Renal damage caused by the 2 systems was compared 1 week after shock wave application. RESULTS: Enhanced fragmentation efficiency was achieved at a delay of 250 microseconds. In vivo results indicate that the dual pulse shock wave generator does not produce more kidney tissue damage. CONCLUSIONS: Tandem lithotriptors may improve the quality and rate of stone comminution without increasing tissue damage. The device enhances cavitation induced damage to kidney stones. Extensive in vivo experiments will be important to evaluate the new design.