An optimal protocol for shock wave delivery by the dual-pulse lithotripter

Dual pulses, generated by opposing, confocal, and simultaneously triggered electrohydraulic shock wave sources, can be used to localize and intensify cavitation for application to lithotripsy. It has been reported that the dual-pulse lithotripter (DPL) may be a safer and more effective lithotripter [Sokolov et al., J. Acoust. Soc. Am. 100 (2001)]. Fragmentation of cement stones and hemolysis in dilute suspensions of human red blood cells were assessed at several positions along the focal axis of the DPL. Pulse repetition frequency was varied from 0.5 to 2 Hz and charging voltage was varied from 12 to 20 kV. At 1 Hz and 15 kV, the number of stone fragments > 1.5 mm, at the focus, remained the same while hemolysis, 2 cm away, decreased by one-half, when compared to the conventional lithotripter at the same PRF and a higher voltage of 18 kV. By varying PRF and voltage, an optimal in vitro protocol for shock wave delivery that maximizes stone fragmentation at the focus and minimizes hemolysis away from the focus might be determined. Results support the hypothesis that cavitation plays a more significant role than shock waves in both stone fragmentation and cell damage in the dual-pulse lithotripter. [Work supported by NIH DK43881.]