QUANTITATION OF SHOCK-WAVE CAVITATION DAMAGE IN-VITRO

Acoustic cavitation damage was quantitated using aluminum foil targets placed within 2-mL polypropylene cryovials. The vials contained vario us media tested for their potential to support cavitation and were exp osed to shock waves using an unmodified Dornier HM3 lithotripter. Foil damage, expressed in terms of a ''damage index'', was measured from d igitized light microscopy images by quantitating the spread of gray-sc ale histograms. Target sensitivity was demonstrated by reproducible do se-response curves over the range (1-200 shock waves) commonly used fo r in vitro cell injury studies. Increased shock wave repetition rate r educed the damage index. Untreated foils showed a very low damage inde x (0.001% +/- 0.001%), while treated foils submerged in Ringer buffer yielded significant damage (2.2% +/- 0.3%, p < 0.001). Degassing the b uffer reduced damage to 0.3% +/- 0.1% (p < 0.001). Foils submerged in caster oil showed virtually no damage. These results indicate acoustic cavitation in target damage. Targets immersed in biological fluids (b lood and urine) had significantly less damage than in Ringer. The effe ct of degassing was also evaluated in a red blood cell lysis assay. He moglobin release in degassed preparations was significantly reduced co mpared to nondegassed controls (p < 0.001) and correlated with reduced foil damage index in cell-free vials. These findings characterize a s ensitive method to quantitate acoustic cavitation and implicate a role for cavitation in shock wave lithotripsy-induced cell lysis. (C) 1997 World Federation for Ultrasound in Medicine & Biology.