Abstract:

Peak acoustic pressures and cavitation generated in shock wave lithotripsy (SWL) appear to contribute to both desired stone comminution and undesired injury to surrounding renal tissue. Our dual pulse system, comprised of two opposing, confocal lithotripters and generating simultaneous, converging shock pulses, localizes and intensifies the peak pressures and cavitation. Comparison of cavitation damage to aluminum foil shows an 8-cm stripe of pits produced by a single-pulse lithotripter and a 1-cm stripe of deep pits produced by the dual-pulse lithotripter. 100 dual pulses generated at 15 kV comminuted gypsum stones placed at the geometric focus F2 into 8 times as many fragments and significantly reduced hemolysis in dilute blood 2 and 4 cm off F2 when compared to 200 single pulses generated at 18 kV. Thus the dual-pulse lithotripter enhanced comminution and reduced injury while cutting treatment time in half. Additionally, when cavitation was suppressed by placing the stones in glycerol, the improvement in comminution was reduced to only a twofold increase. This result indicates that the localized and intensified cavitation is the dominant mechanism in the accelerated comminution produced by the dual-pulse lithotripter. [Work supported by NIH Grants Nos. P01-DK43881 and R01-DK55674.]