Effect of dual-reflector lithotripter on stone fragmentation and cell damage

Abstract

An electrohydraulic lithotripter uses an ellipsoidal reflector to focus shock waves on to a kidney stone. The shock wave generates a cylindrical cavitation field, ∼1 cm wide×10 cm long, that has been implicated in both stone fragmentation and damage to healthy tissue during lithotripsy treatment. A dual-reflector lithotripter, consisting of two identical spark-gap lithotripters facing each other and firing simultaneously, creates a more localized cavitation field, ∼3 cm wide×5 cm long (Sokolov, Berlin 1999). Such a field may increase the rate of stone fragmentation while mitigating damage to surrounding tissue. Breakage of model stones at the focus and hemolysis of red blood cells 3 cm from the focus were assessed for both conventional lithotripsy (CL) and dual-reflector lithotripsy (DRL). To equalize total energy input, the number of shots was halved from CL to DRL. Stones subjected to DRL were broken into several major fragments while stones subjected to CL remained intact except for some dust. Human blood was diluted to 3% hematocrit in degassed PBS and placed in acoustically transparent sample tubes. There was no statistical difference in percent hemolysis between CL (5.12±1.01%) and DRL (5.39±0.57%). [Work supported by NIH DK43881 and NSF.]