Shock Wave Lithotripsy: Mechanisms and Amelioration of Vascular Damage

University Of California-Berkeley, Berkeley CA

Investigators

Abstract

0201921 Szeri In current clinical practice, Shock Wave Lithotripsy (SWL) is routinely used for treatment of urolithiasis (kidney stones). It also causes acute renal injury: including hemorrhage, hematoma and edema. The rupture of small blood vessels is a primary feature of vascular injury associated with SWL. The potential mechanisms are: stretching and rupture of vessels by growth of constrained bubbles, or damage of vessel walls by asymmetric collapse of constrained cavitation bubbles, and possibly damage of vessel walls by attack of free radicals produced in the bubble collapses. Prior work has shown that bubbles are associated with phantom vessel damage by an XL-1 lithotripter in vitro . However, there is doubt as to the precise mechanism of damage. Prior work has also shown that, to compare well with experiments, vapor dynamics need to be included in SWL bubble simulations. A simulation has been developed of non-spherical collapses including heat and vapor transfer. A slight modification to a Dornier HM-3 clinical lithotripter can reduce problematical bubble growth and thus decrease the potential for vascular injury in SWL while maintaining satisfactory stone comminution. Finally, the investigators have developed an analytical theory and computer simulation of the focusing of spherical compression waves into shocks, even where there are strong material inhomogeneities. The first goal of the proposed research is to determine the mechanism of damage by bubbles in blood vessels interacting with lithotripter shock waves (LSW). The second goal is to develop a rational procedure to optimize the compression wave that becomes the LSW, so as to minimize the potential for bubble growth while maintaining stone comminution. Both goals will be reached through theory, simulation and experiment.