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目的通过数值模拟研究体外冲击波粉碎结石术(extracorporeal shock wave lithotripsy,ESWL)中单脉冲与双脉冲两种不同情况下的压力场,并对两者结果进行比较和分析。方法利用2D轴对称Euler方程和混合网格改进的时空守恒元解元(space-time conservation element and solution element,CE/SE)数值格式,对ESWL中冲击波水下传播的压力场进行模拟。结果 CE/SE方法成功地追踪了冲击波波阵面传播情况,数值解较好地展示了ESWL焦点附近的冲击波聚焦特性:在焦点附近双脉冲产生的压力峰值约为单脉冲的两倍,越靠近焦点处双脉冲ESWL所得到的碎石效率相较于单脉冲时越高,且在焦点附近产生正压随后出现了绝对值极高的负压。结论采用液电双脉冲波源机型能够有效地提高碎石效率,并且冲击波聚焦时出现空化是不可避免的。上述结论为ESWL碎石机的设计制造及临床应用提供了可靠的数值模拟结果。
Objective To study the pressure fields in two kinds of extracorporeal shock wave lithotripsy (ESWL) by means of numerical simulation and to compare and analyze the two results. Methods The pressure field of ESWL underwater shock wave propagation was simulated by using the 2D axisymmetric Euler equation and the improved space-time conservation element and solution element (CE / SE) numerical scheme. Results The CE / SE method successfully tracked the shock wave propagation. The numerical solution better shows the shock wave focusing characteristics near the focus of the ESWL. The double pulse near the focus generates about two times the peak pressure of a single pulse. Double-pulse ESWL at the focal point resulted in higher gravel efficiency compared to single pulse and positive pressure near the focal point followed by a very negative pressure of absolute high. Conclusion The dual-pulse liquid-electric source model can effectively improve the lithotripsy efficiency, and the cavitation during the shock wave focusing is inevitable. The above conclusions provide reliable numerical simulation results for the design, manufacture and clinical application of the ESWL lithotripsy machine.