胸主动脉夹层血液两相流动数值模拟

发布时间：2018-03-21 07:18

本文选题：主动脉夹层　切入点：双流体　出处：《浙江大学》2017年硕士论文　论文类型：学位论文

【摘要】：胸主动脉夹层是一种严重危害人类健康的心血管疾病。近年来胸主动脉腔内修复术(TEVAR)有效降低了 Stanford B型主动脉夹层的死亡率,已成为治疗该种疾病的首选方式。以往研究表明,即便在TEVAR治疗后,夹层破裂和内脏动脉缺血仍是患者致死的主要原因。然而对于夹层发生、发展和破裂机制,目前尚缺乏足够的认识,这给临床治疗带来了很大的困难。为了深入研究这一问题,本文提出发展血液两相流动,结合双流体模型和任意拉格朗日-欧拉(ALE)方法,同时处理血液两相流动及复杂边界流固耦合作用,来弥补以往研究中将'血液当作单相牛顿流体和将血管壁当作刚性壁面的不足。本文旨在通过计算得到血液流速、壁面剪切应力等一系列血流动力学参数,并依据结果分析红细胞、血流动力学参数与血栓形成、夹层假腔重塑之间的关系,为术后预测夹层发展、评估TEVAR治疗效果提供数据参考。主要工作内容包含以下三个部分:第一部分首先对CT断层扫描图像进行处理,建立真实的三维胸主动脉夹层模型。其次对采用的双流体模型进行数值验证,结果表明本文应用的双流体模型能准确模拟血液两相流动。接着应用双流体模型和ALE方法对一例Stanford B型胸主动脉夹层模型进行数值模拟,发现采用流固耦合模型计算得到的壁面平均剪切应力低于刚性壁面计算结果,最大相差18.4%。第二部分是对一例左锁骨下动脉(LSA)封堵的急性夹层病例进行TEVAR术前及术后的血液流动数值模拟,发现术后真腔和主动脉弓血管分支的血流量显著增大,分别由术前11.15%、14.85%的分流比增加到术后的51.49%和37.32%,反映出TEVAR对真腔及分支血管供血功能的明显改善作用。并通过模拟一例虚拟构建的LSA未封堵术后模型发现,LSA封堵对上肢供血影响不大,证明了临床上大多患者对LSA封堵良好耐受的情况。第三部分是对一例已发生瘤样扩张的慢性夹层病例进行TEVAR术前及术后的血液流动数值模拟,发现术后降主动脉血液流动更稳定,湍流强度、OSI值远低于术前,TEVAR能有效降低假腔扩张破裂的风险,同时改善真腔内流动稳定性及远端供血。
[Abstract]:Thoracic aortic dissection is a serious cardiovascular disease harmful to human health. In recent years, endovascular repair of thoracic aorta has effectively reduced the death rate of Stanford type B aortic dissection. Has become the preferred treatment for this disease. Previous studies have shown that dissection rupture and visceral artery ischemia are the leading causes of death even after TEVAR treatment. At present, there is a lack of sufficient understanding, which brings great difficulties to clinical treatment. In order to study this problem in depth, a two-phase blood flow model, combined with a two-fluid model and an arbitrary Lagrangian Euler Ale method, is proposed in this paper. At the same time, the two-phase flow of blood and the fluid-solid coupling with complex boundary are processed to make up for the deficiency of the previous researches that 'blood is regarded as a Newtonian fluid and a wall of blood vessel as a rigid wall.' the purpose of this paper is to obtain the velocity of blood flow by calculation. A series of hemodynamic parameters, such as wall shear stress, were used to analyze the relationship between erythrocyte, hemodynamic parameters and thrombus formation and false cavity remodeling in order to predict the development of dissection after operation. The main work includes the following three parts: in the first part, CT tomography images are processed. A real three-dimensional thoracic aortic dissection model was established. Secondly, the two-fluid model was numerically verified. The results show that the two-fluid model can accurately simulate the two-phase blood flow. Then, a case of Stanford B type thoracic aortic dissection model is numerically simulated by using the two-fluid model and ALE method. It is found that the average shear stress of the wall calculated by the fluid-solid coupling model is lower than that of the rigid wall. The second part was the numerical simulation of blood flow before and after TEVAR in an acute dissection patient with left subclavian artery occlusion. The shunt ratio increased from 11.15% before operation to 51.49% and 37.32 after operation, respectively, reflecting the obvious improvement of TEVAR on the function of blood supply of true cavity and branch vessels. The effect of limb blood supply was not significant. The results show that most patients have good tolerance to LSA occlusion. The third part is the numerical simulation of blood flow before and after TEVAR in a case of chronic dissection with tumor-like dilatation. It was found that the blood flow of descending aorta was more stable after operation, and the OSI value of turbulence intensity was much lower than that of preoperative Tevar, which could effectively reduce the risk of dilatation and rupture of pseudolumen, and improve the stability of intraluminal flow and distal blood supply.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：R543.1

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