American Journal of Roentgenology, Vol 155, 1211-1216, Copyright © 1990 by American Roentgen Ray Society
Piezoelectric biliary lithotripsy: an in vitro study of factors affecting gallstone fragmentation
SJ Schulte and RL Baron
Department of Radiology, University of Washington Medical Center, Seattle 98195.
Factors affecting the fragmentation of gallstones with piezoelectric
lithotripsy were studied in vitro, with a goal of providing data that will
help direct treatment with piezoelectric lithotriptors. Two hundred
fifty-seven stones from 50 patients were treated with the EDAP LT.O1
lithotriptor until all fragments measured 2 mm or less in diameter. The
fragmentation process was observed, and two patterns were evident: central
fragmentation and peripheral chipping. The majority of stones fragmented
centrally. Fragmentation characteristics in different stones from the same
patient were compared with those from different patients. Stone diameter,
shock-wave frequency and power, and CT appearance were examined and
correlated with fragmentation. Gallstones from the same patient showed
uniform fragmentation patterns and consistent relationships between
fragmentation time and gallstone size, shock-wave frequency, and power. In
stones from the same patient, gallstone size had a marked effect on
fragmentation time, which correlated with the cube of the stone diameter,
and shock-wave frequency and power had a proportional inverse linear
relationship with fragmentation time. When controlling for stone size and
treatment parameters, stones from multiple patients showed marked
differences in fragmentation time, and because of this, poor correlation
between stone size and fragmentation time. Stones grouped according to CT
pattern and attenuation showed wide variation and no correlation between CT
characteristics and fragmentation pattern or fragmentation time. Our
results show that a great variability exists in fragmentation time of
gallstones, making it impossible to accurately predict fragmentation time
at a given stone size. Only rough estimates of longer fragmentation times
with increasing stone size can be made. The linear relationships between
shock-wave frequency or power and fragmentation time allow one to easily
predict the effect of manipulating these variables and to tailor treatment
to each patient's tolerance. Finally, CT appearance does not appear to be
predictive of fragmentation outcome.