Design and characterization of a research electrohydraulic lithotripter patterned after the Dornier HM3

An electrohydraulic lithotripter has been designed that mimics the behavior of the Dornier HM3 extracorporeal shock wave lithotripter. The key mechani cal and electrical properties of a clinical HM3 were measured and a design implemented to replicate these parameters. Three research lithotripters hav e been constructed on this design and are being used in a multi-institution al, multidisciplinary research program to determine the physical mechanisms of stone fragmentation and tissue damage in shock wave lithotripsy. The ac oustic fields of the three research lithotripters and of two clinical Dorni er HM3 lithotripters were measured with a PVDF membrane hydrophone. The pea k positive pressure, peak negative pressure, pulse duration, and shock rise time of the focal waveforms were compared. Peak positive pressures varied from 25 MPa at a voltage setting of 12 kV to 40 MPa at 24 kV. The magnitude of the peak negative pressure varied from -7 to -12 MPa over the same volt age range. The spatial variations of the peak positive pressure and peak ne gative pressure were also compared. The focal region, as defined by the ful l width half maximum of the peak positive pressure, was 60 mm long in the a xial direction and 10 mm wide in the lateral direction. The performance of the research lithotripters was found to be consistent at clinical firing ra tes (up to 3 Hz). The results indicated that pressure fields in the researc h lithotripters are equivalent to those generated by a clinical HM3 lithotr ipter. (C) 2000 American Institute of Physics. [S0034-6748(00)01806-2].