【作者】 韦春霞；

【导师】 陈景秋；

【作者基本信息】 重庆大学 ， 流体力学， 2010， 博士

【摘要】 1980年诞生的体外冲击波粉碎结石技术ESWL(Extracorporeal Shock Wave Lithotripsy)是医疗技术领域一项重大成就。ESWL通过水下放电或爆炸产生冲击波,利用聚焦冲击波的高能量密度和空化作用粉碎患者体内肾结石,因其使用便捷,粉碎效率高,无外科手术侵入创伤和低廉的治疗费用等特性,自出现后即迅速成为治疗尿路结石的最常用临床手段。尽管如此,ESWL也有需要完善之处。在临床和实验研究中均发现伴随着ESWL的不同形式损伤,例如血尿、慢性出血、多重肾软组织内的血肿、以及肾水肿等。在冲击波医疗技术中,医疗效率和安全性同等重要。为了ESWL碎石效率最优化和组织损伤最小化,确定聚焦冲击波的动力学焦点,研究负压的演化过程以及空化显得极为重要。本文在国家自然科学基金(20472316)和教育部博士点专项基金(20070611004)的资助下,完成了冲击波聚焦过程、空化效应产生和负压演化过程的数值模拟,为提高压电式和液电式ESWL碎石机的碎石效率和减少副作用,以及设计制造和临床应用方面提供了科学的参考依据。冲击波是一种非线性波。对于它,关于线性波的Snell反射定律等物理定律不再成立。水下冲击波聚焦的数值研究需要考虑水的可压缩性。本文采用Tait状态方程来描述水的特性,并假设水是无粘的、运动中无热传导和热辐射。这样就可以借助空气动力学中研究冲击波的一系列方法,来研究ESWL中的水下冲击波传播、反射和聚焦。一般认为ESWL冲击波的负压波段是引起水空化的主要原因。CCW(Chester-Chisnell-Whitham)方法即Whitham的激波动力学方法,是一种近似方法,在一定条件下对激波面的追踪计算简单而有效,可完整地描述波阵面的演化过程。本文编写了CCW方法的程序,完成了球面压电陶瓷型ESWL的冲击波传播的波阵面的数值追踪,为压电陶瓷式ESWL碎石机的设计制造和临床应用提供了科学依据。CE/SE(Space-time Conservation Element and Solution Element)方法即时空守恒元和解元方法,1995年被提出,具有稳定性好、计算量小、计算结果精度高和对间断分辨率高等特点,已被美国NASA列为第二代CFD程序中的主要算法之一。本文通过适当改造张增产等的改进CE/SE方法来离散Euler方程,建立了研究ESWL中的水下聚焦冲击波的二维数学模型,分别对于球面压电陶瓷型和液电式机型ESWL的在单侧和双侧波源情况下,冲击波传播过程完成了数值模拟。本文还利用CE/SE方法,用连续模型来描述空化流动,分别以Liu model和Cut-off model作为状态方程,对一维管道中不同初始条件下发生空化流动时的压强、速度、和密度的分布进行了数值模拟。数值结果表明:1.ESWL中冲击波的动力学焦点(非线性焦点)一般并非几何焦点(线性焦点),而是有所偏移。因此,在临床应用球面压电陶瓷型ESWL粉碎结石时,实际焦点应当规定为压力最大的点,而不是简单地就将几何焦点选为轰击的靶点。2.本文首次将CE/SE方法应用于空化问题的研究。数值结果表明CE/SE方法是研究空化问题的一种有效方法。3. ESWL产生的冲击波聚焦时出现空化是不可避免的。所以在EWSL的设计制造及临床应用中,都不可忽视空蚀。除了使用通用作图软件外,本文中所有数值模拟程序都是作者用Fortran语言自行编写的。更多还原

【Abstract】 Extracorporeal Shock Wave Lithotripsy (ESWL) invented in 1980 is one of the most significant achievements of modern medical treatment technology. The kidney stone inside the patient can be broken down into small fragments, by firing shock waves with high energy density and cavitation effect by underwater discharge or explosion during the ESWL treatment. Since ESWL emerged, due to its convenience of the treatment, high efficiency of the stone comminution, without invasive damages of surgery, less clinical costs and etc., it has rapidly become the most common clinical treatment of kidney stone disease. However, ESWL still should be improved, because the side effects, different short- and long-term damages, are observed by the clinical use and laboratory researches of ESWL.A common side effect of the ESWL treatment is the presence of blood in the urine (hematuria). There are others too, such as chronic hemorrhage, hematoma in kidney parenchyma, kidney edema and etc.. Therefore, both efficiency and security of the treatment are very important for the shock wave therapy. In order to maximize the efficiency of stone comminutions and minimize the side effects in the ESWL treatment, it is especially meaningful to locate exactly the dynamical focus of shock waves and to gain good insight in the evolution of the negative pressure as well as the cavitation effect. With the support of National Natural Science Foundation of China(20472316)and Doctoral Fund of Ministry of Education of Chin(a20070611004), we completed the numerical simulations of the process about shock wave focusing and negative pressure evolution, and the numerical simulations of cavitation. In this paper some important scientific data to maximize stone comminution and decrease tissue damage of the piezoelectric and the electro-hycaulic ESWL are shown. The data are relevant to design, manufacture and clinical applications of ESWL.Shock wave is a nonlinear wave, for which some physical laws of the linear waves, such as Snell reflection law, are valid no more. For the numerical research of focusing of underwater shock waves the compressibility of water must be considered. In this paper, the characters of water were described by Tait’s state equation. It was also supposed that water was inviscid and there was no heat conduction or radiation during the movement. So by the help of the methods of shock wave of gas dynamics, we could investigate the propagating, reflecting and focusing of the underwater shock waves in ESWL. The negative pressure waves of the underwater shock wave in ESWL are generally considered as the main cause of the cavitations.CCW (Chester-Chisnell-Whitham) method of Whitham’s shock wave dynamics is an approximation. It is simple but effective in the tracing the shock wave fronts under some conditions. CCW method can be utilized to describe all the nonlinear process of the shock wave front. In this paper, a numerical code of the geometric shock wave dynamics method CCW was made and applied to track the successive positions of the fronts of shock waves of the spherical piezoelectric ESWL. Some important scientific results to design, manufacture and clinical application of the piezoelectric lithotripter were given.CE/SE (space-time conservation element and solution element) method, proposed in 1995, is already become one of the primary methods in the second generation of the CFD scheme of NASA, due to its good stability, calculation accuracy and high resolution. Based on the appropriate transformation to Zhang’s modified CE/SE method in order to discrete Euler equations, in this paper a two-dimensional numerical model of the studying to the underwater focusing shock wave of ESWL was supposed, and the flow fields of shock waves were numerically simulated for one-side source and both-side wave sources of both piezoelectric and electric-hydraulic ESWL. In this paper, moreover, by the CE/SE method the cavitation flow was described with the continuous model, using Liu model and Cut-off model as the state equation respectively, to the numerical simulation of the pressure, speed, and density distribution of the one-dimensional channels in different initial conditions when there were cavitation flow.Numerical results show that: 1. The dynamic (non-linear) focus of the shock wave is generally different from the geometric (linear) focus in ESWL, there is often some deviation. Therefore, in the clinical treatment of spherical piezoelectric ESWL, the actual focus should be defined as the greatest pressure point and located as the target of firing, rather than the geometric focus. 2. It is the first time to apply CE / SE method to the problems of cavitation in this paper. The numerical results show that the CE / SE method is an effective method to study of cavitation. 3. The cavitations are inevitable during the focusing of shock waves in EWSL, therefore, for the design, manufacture and clinical applications of EWSL cavitation can not be ignored.All the numerical simulation programs except graphic software are written by the author with the FORTRAN.更多还原