Use of Surfactant Enhances Cavitation Effect in Extracorporeal Shock Wave Lithotripsy*

An in vitro study was designed to test the hypotheses that lowering the surface tension in the fluid medium will induce larger cavitation bubbles during extracorporeal shock wave lithotripsy (SWL) and that the same action will lead to a greater number of smaller equilibration bubbles. Together, these changes could increase the efficiency of SWL. Sodium dodecyl sulfate (SDS) was used in concentrations of 0 to 95% of the critical micellar concentration (CMC). The targets, made of heavy-duty aluminum foil, were treated in the Sonolith 3000 with 50 shocks. The size distribution of the craters produced widened with increasing concentrations of SDS, and the average size of the craters increased, implying an increase in the size of the bubbles and resulting microjets. This result in turn suggests an increase in the energy stored in the bubbles, which would then be available to destroy stones. These findings may be exploitable to reduce the number of shocks needed in SWL.