Sapozhnikov Oleg A, Maxwell Adam D, MacConaghy Brian, Bailey Michael R
Department of Acoustics, Physics Faculty, Moscow State University, Leninskie Gory, Moscow, 119992, Russia.
J Acoust Soc Am. 2007 Feb;121(2):1190-202. doi: 10.1121/1.2404894.
In vitro experiments and an elastic wave model were used to analyze how stress is induced in kidney stones by lithotripsy and to test the roles of individual mechanisms-spallation, squeezing, and cavitation. Cylindrical U30 cement stones were treated in an HM-3-style lithotripter. Baffles were used to block specific waves responsible for spallation or squeezing. Stones with and without surface cracks added to simulate cavitation damage were tested in glycerol (a cavitation suppressive medium). Each case was simulated using the elasticity equations for an isotropic medium. The calculated location of maximum stress compared well with the experimental observations of where stones fractured in two pieces. Higher calculated maximum tensile stress correlated with fewer shock waves required for fracture. The highest calculated tensile stresses resulted from shear waves initiated at the proximal corners and strengthened along the side surfaces of the stone by the liquid-borne lithotripter shock wave. Peak tensile stress was in the distal end of the stone where fracture occurred. Reflection of the longitudinal wave from the distal face of the stone--spallation-produced lower stresses. Surface cracks accelerated fragmentation when created near the location where the maximum stress was predicted.
采用体外实验和弹性波模型分析了冲击波碎石术在肾结石中诱导应力的方式，并测试了剥落、挤压和空化等个体机制的作用。圆柱形U30水泥结石在HM-3型碎石机中进行处理。使用挡板来阻挡导致剥落或挤压的特定波。在甘油（一种抑制空化的介质）中测试添加了模拟空化损伤的有和没有表面裂纹的结石。每种情况都使用各向同性介质的弹性方程进行模拟。计算得到的最大应力位置与结石断裂成两块的实验观察结果吻合良好。计算得到的较高最大拉应力与断裂所需的冲击波次数较少相关。计算得到的最高拉应力是由在近端角落引发并由液体传播的冲击波碎石机冲击波沿结石侧面增强的剪切波产生的。峰值拉应力位于结石发生断裂的远端。结石远端表面的纵波反射——剥落——产生的应力较低。当在预测的最大应力位置附近产生表面裂纹时，会加速破碎。
