[Quantitative evaluation of cavitation bubble fields induced by lithotripter shock waves]

Extracorporeal shock wave lithotripsy is the world-wide standard therapy for renal stones. The rare-faction phase of the shock wave can induce cavitation within the body. Cavitation contributes to stone disintegration but also to medical side effects. The aim of this study was to evaluate the spatial and size distribution of the cavitation bubble fields. To this end, the bubble fields were photographed digitally and evaluated automatically by image processing. The influence of various medium (water) and shock wave parameters was investigated. Water purity, i.e. the number of cavitation nuclei, was the most critical medium parameter which has to be controlled. At oxygen levels higher than 4 mg/l, cavitation increased rapidly when high shock wave frequencies of 2 Hz were used.