| Research Abstract |
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
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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 data
As 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
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