Conversion of an HM3 lithotripter into a research device

PURPOSE: To describe the conversion of a Dornier HM3 lithotripter into a research device and evaluate its performance. MATERIALS AND METHODS: A used HM3 lithotripter was donated to our university by the St. Thomas' Hospital in London. It was disassembled, shipped to our laboratory, partially assembled, and modified as a research lithotripter. Pressure measurements at several positions and kidney stone model fragmentation tests were performed to evaluate the modified system. Results were compared with information published by other authors and data obtained in our laboratory using another electrohydraulic research lithotripter. RESULTS: Pressure records showed typical lithotripter waveforms with a rapid rise to about 50 MPa, followed by decay to a negative peak of approximately 9 MPa. Maximum compressional peaks were obtained at F2 and 25 mm below F2. Kidney stone model fragmentation was typical for electrohydraulic shockwave lithotripters. CONCLUSIONS: Comparison of pressure measurements with data obtained by other authors on the same lithotripter several years ago indicate that the pressure waveform has not changed significantly. A much smaller water tank, a small X-Y-Z positioner, and no X-ray imaging system facilitate the use of this shockwave generator for in vitro experiments with small samples such as vials containing cell suspensions, having the advantage of a reliable, well-known, and well-characterized commercial shockwave generator.