Experiences with lithotripters: measurements of standardized fragmentation.

A comparison of lithotripters in terms of the fragmentation efficacy was established by using artificial stones. Two hundred pulses were applied to identical calcium sulphate cubes at varied energy levels of different lithotripters. In the cubics the shock waves formed regular craters, which could be analyzed with regard to depth, diameter, and volume. Dimensions of the craters increased with increasing energy. Each shock wave source designed a typical crater form. Different efficacies of fragmentation within different lithotripters could be recognized. High focal peak pressures did not guarantee better fragmentation effects. By using different acoustic lenses in the same electromagnetic lithotripter, the influence of different focus zones of the shock wave on the fragmentation could be investigated without any changes of the energy input. Results clearly emphasize the possibility of an increase of fragmentation efficacy by changing only the focal zones and the distribution of energy within the focal area.