| Summary: | 碩士 === 中原大學 === 生物醫學工程研究所 === 101 === It is well known that carotid artery stenosis is the major factor causing ischemic stroke. Clinically, diagnosis for carotid artery stenosis is determinated by the sufficiency of blood supply to the brain. There are two types of carotid artery stenosis, however, no investigations emphasized the impact between their differences. Previous studies have focused on the degree of stenosis over 70% and less on the mild one lower than 30%. Accordingly, a stenosis model we built with a simulation method which is based on a carotid artery computer tomography image from a healthy adult with age 50. Several degree of stenosis (e.g. 10%, 30%, 50%, 70% and 90%) are generated and categorized into concentric or eccentric type. The boundaries have introduced to the values collected from the published clinical references. In addition, to address the correlation with the information from simulation method and clinical references we have also developed in vitro carotid artery models of normal, concentric and eccentric stenosis conditions. The later two conditions contained 30% and 70% degree of stenosis respectively. Furthermore, the dynamics of flow field is observed by application of three different color dyes to the in vitro model.
The results suggest that the blood flow decreases while the degree of stenosis increases in both concentric and eccentric conditions. Eccentric stenosis has more significant turbulence and wall shear stress. In mild and moderate (30% to 50%) degree of stenosis, recirculation, streamwise vortex and secondary flow are initially occurred especially under the view of hydromechanics. Similarly, in vitro model shows that recirculation and streamwise vortex have significantly enhanced in a stenosis degree dependent manner, which are consistent with the numerical results. Besides, the blood pressure of internal carotid artery is reduced with an increase in stenosis degree, which is more significant in concentric stenosis type.
This study demonstrates that the variation of flow field differs between concentric and eccentric type of stenosis. Existence of turbulence appears in the mild and moderate degree of stenosis. Variation of internal carotid artery blood pressure is opposite between two types of stenosis. Hence, this study could be able to provide a powerful medical evaluation before carotid endarterectomy and carotid artery stenting.
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