Hemodynamic factors play important roles in the formation, progression and rupture of cerebral aneurysms, and the Wall Shear Stress (WSS) and Oscillatory Shear Index (OSI) on the aneurysms are considered to be correlated with their growth and rupture. In this article, two computational models based on patient-specific cerebral aneurysms with daughter saccule are constructed from 3D-RA image data, one is lateral aneurysm located in middle cerebral artery (CA1) and the other is terminal aneurysm located in anterior communicating artery (CA2), The corresponding models of the two aneurysms by removing daughter saccule are established in order to investigate the initiation and growth of the daughter saccule. The flow patterns and the distributions of hemodynamic factors in the two aneurysms before and after daughter saccule is removed are obtained by solving the governing equations with the commercial CFD software Ansys CFX11.0 under the non-Newtonian fluid assumption. By analyzing the flow patterns, it is concluded that the aneurysms with daughter saccules have more complex and unstable flow patterns and hence are prone to rupture. By comparing the distribution of OSI, a hypothesis that a high OSI causes the growth of the daughter saccule is presented.
WANG Sheng-zhangCHEN Jia-liangDING Guang-hongLU GangZHANG Xiao-long
Hemodynamic characteristics such as blood velocity,blood pressure,flow impingement,wall shear stress and oscillatory shear index are considered to play important roles in the initiation,growth,rupture and recurrence of the cerebral aneurysms.Endovascular therapy is widely implemented to treat the cerebral aneurysms by releasing coils into the aneurysm sac for limiting the blood flow to the sac and stent-assisted coil embolization is adopted to occlude the wide-necked or complex aneurysms.Some researchers believe that stents are not only a mechanical device but may act as a biological system and contribute to vessel wall healing.Hemodynamics simulation helps people understand the effect of hemodynamic characteristics on the recurrence of the coiled aneurysm and it also benefits the interventional planning of neurosurgeons.This study constructed the numerical model for a subject-specific ICA aneurysm treated with stent-assisted coil embolization,which combined the coiled model of the aneurysm with a porous stent placement,and simulated the pulsatile blood flow in these aneurysm models.When a stent was placed across the aneurysm orifice in the coiled aneurysm,the high wall shear stress around the distal aneurysm root was reduced more than that of the coiled aneurysm without a stent.The simulated results point to the conclusion that the stent not only protects the parent artery from occlusion due to extension of coils or thrombosis,but may also reduce the recurrence risk of the stent-assisted coiled aneurysm.
WANG ShengZhangZHANG YiSenLU GangYANG XinJianZHANG XiaoLongDING GuangHong
