What makes a shock wave efficient in lithotripsy?
The aim of this investigation was the connection of quantitative shock wave parameters to stone fragmentation in lithotripsy.  We developed an in vitro procedure where eroded craters in artificial stones could be measured with respect to their geometric outlines.  By altering the components of an electrodynamic ultrasonic source we obtained a multitude of shock wave foci with physical parameters covering a wide range.  With these foci different craters were formed and measured.  With a correlation method the quantitative stone erosion could be connected with single physical parameters of the shock waves.  As a result we found strict linear dependence of the volume erosion on the effective energy.  On the other hand, the peak pressure in the focus revealed to be a poor parameter to qualify the fragmentation efficiency of a lithotripter.  Additionally the contribution of the rise time of the shock wave to stone erosion is of negligible influence.
Granz
B
B
Forschungslabor, Siemens AG, Erlangen, Germany.
Köhler
G
G
D004867:Equipment Design; D006801:Humans; D007669:Kidney Calculi / Q000628:therapy; D008096:Lithotripsy / Q000295:instrumentation*; D055585:Physical Phenomena; D010825:Physics