Computational study of rupture of the cerebral aneurysms

蛛网膜下腔出血的主要原因是脑动脉瘤破裂。一旦发生蛛网膜下腔出血，有很高的死亡风险。当发现脑动脉瘤时，由于在目前的情况下无法预测其破裂，通常进行手术治疗。然而，脑动脉瘤的手术是困难的，不仅给病人带来身体上的负担，而且给病人带来经济上的负担。因此，预测个别动脉瘤破裂的危险因素，以防止不必要的手术是非常重要的。本研究旨在探讨脑血管几何与血流动力学之间的关系，以预测脑动脉瘤的破裂和形成。该项目的研究人员正在开发一个数值模拟系统，该系统由基于医学图像的几何建模、网格生成、有限元流体模拟和科学可视化组成。一个数据库系统的设计是为了组织和分析医学图像，更多的生理，和计算机图形或电影的数值结果，为循证医学的目的。此外，由于模拟系统将动脉壁假设为刚性壁，因此研究了数值方法来处理血流-动脉壁相互作用问题的有效方法。本课题主要研究三个课题：1)基于医学图像的模拟与数据库系统的开发；2)血流-动脉壁相互作用的数值模拟；3)数值结果与临床数据的比较。课题1)对大脑中动脉（MCA）连接处进行了19例数值模拟。利用血管几何参数建立数据库系统，并利用19例病例的结果进行多变量分析，估算出最大管壁剪应力。计算结果与数值分析结果吻合较好。研究发现，中动脉直径、分支直径与中动脉直径之比以及中动脉与分叉动脉之间的分叉角是决定最大壁剪应力的重要几何因素。在主题2)中，提出了血流与动脉壁相互作用的数值计算方法。将该方法应用于弯曲管模型和颈内动脉模型。结果表明，尽管动脉壁的变形很小，但弹性动脉壁对管壁剪切分布的影响是显著的。最后，对于题目3)，我们对日本东京大学20年的调查结果进行了总结，以研究未破裂动脉瘤与蛛网膜下腔出血之间的关系。少

A main cause of subarachnoidal hemorrhages is rupture of a cerebral aneurysm. Once the subarachnoidal hemorrhage occurs, there is a high risk of death. When the cerebral aneurysm is found, it is usually operated because its rupture can not be predicted under the present circumstance. However, an operation of the cerebral aneurysm is difficult and gives not only physical but also financial burdens to a patient. Thus it is quite important to predict a risk factor of individual aneurysm's rupture in order to prevent unnecessary surgeries.The research aims to investigate the relationship between cerebrovascular geometry and hemodynamics in order to predict rupture and creation of cerebral aneurysms. The investigators of the project have been developing a numerical simulation system, which consists of medical image-based geometric modeling, grid generation, finite element fluid simulation, and scientific visualization. A database system is designed so as to organize and analyze medical imag … More es, physiological, and computer graphics or movies of numerical results for the purpose of evidence-based medicine. In addition, since the simulation system assumes the arterial walls as rigid walls, numerical methods are investigated for an effective way to treat blood flow-arterial wall interaction problems.The present research project focuses on the following three topics : 1) Development of medical image-based simulation and database system 2) Numerical simulation of blood flow-arterial wall interaction 3) Comparison of numerical results with clinical dataAs for the topics 1), a total of 19 cases of numerical simulations are conducted for the middle cerebral artery (MCA) junction. The database system was constructed using vascular geometric parameters, and the multivariate analysis is performed using the results of 19cases to estimate a maximum wall shear stress. The results are compared and show good agreement with those of numerical analysis. It is found that diameter of the MCA, ratio of diameter of branching to that of the MCA, and difurcation angle between the MCA and brunching arteries are important geometric factors in determining maximum wall shear stresses. As for the topics 2), a numerical mothod for interaction between blood flow and arterial wall is developed. The method was applied to the curved pipe model and the Intermal Carotid artery model. As a result, it is found that effects of elastic arterial wall on the wall shear distribution is significant despite a small deformation of the arterial wall. Finally, for the topics 3), the survey had been conducted for 20 years at Teikyo University, and the results were summarized to study the relationship between unrupture aneurysms and subarachnoidal homerrhages. Less