Dynamic behavior of bubbles during extracorporeal shock-wave lithotripsy

The interaction of air bubbles attached to gelatin surfaces, extirpated livers or abdominal aortas of rats with underwater shock waves was investigated to help clarify the tissue-damage mechanism associated with cavitation bubbles induced during extracorporeal shock-wave lithotripsy. The overpressure of the shock wave was 10.2±0.5 MPa. The initial bubble radii varied from 0.12 to 3.06 mm. The subsequent collapse of the bubbles was recorded by a high-speed camera. The liver-cell damage was histochemically evaluated. The bubble attached to gelatin or rat's liver surface migrates away from the surface with an oscillatory growth/collapse behavior after the shock-wave interaction. The penetration depth of the liquid jet into the gelatin and the radius of the subsequent damage pit on the surface depend on the initial bubble radius. The elongation and split of the nuclei in the liver parenchymal cells in the direction of the liquid jet and the increase in the cell density within the circumference of the injured region are revealed histologically.