IN-VITRO GALLSTONE FRAGMENTATION BY 3 PIEZOELECTRIC LITHOTRIPTERS

Several different piezoelectric lithotripters have been under clinical investigation for gallstones in the USA. Design differences in the di fferent shock wave generators result in different characteristics for the three devices and different peak pressures at the focus of the lit hotripters. Using gallstone families, we sought to study fragmentation in the three lithotripters. A total of 56 gallstones from eight galls tone families were studied. Forty-eight stones were fragmented in thre e lithotripters (16 in each), Diasonics (Therasonic), EDAP (LT01), and Wolf lithotripter (Piezolith 2300), at maximum power and a rate of 2- 2.5 Hz. A total of 500 shocks was applied to each stone in each of the three lithotripters. Gallstone composition was determined by infrared spectroscopy on one stone of each family (8 x 1). Initial stone weigh t and size were similar in all the three groups. All families consiste d of cholesterol stones (> 70% cholesterol). The fraction of the initi al stone mass reduced to fragments less-than-or-equal-to 2 mm was not significantly different in the three lithotripters (Diasonics [n = 16] = 60 +/- 4%, EDAP [n = 16] = 53 +/- 6%, Wolf [n = 16] = 50 +/- 7%; p = 0.068). When fragmentation was calculated as the fraction of initial mass reduced to particles less-than-or-equal-to 4 mm, the fraction fo r the Wolf device (which has the highest reported peak pressure) was 5 9 +/- 7% (n = 16), and was significantly poorer than the Diasonics, 79 +/- 5%; n = 16, p = 0.013), and the EDAP 74 +/- 8% (n = 16; p = 0.035 ). There was considerable variability in fragmentation between stones of different families (55%-93%) but only small differences were seen b etween members of a given family tested in different lithotripters (9% -20%). Families that fragmented poorly did so in all three lithotripte rs and those that fragmented well did so in all lithotripters. Our dat a suggest that the material properties of gallstones are a major deter minant of fragmentation with piezoelectric lithotripters.