Three-dimensional Numerical Simulation Of Hemodynamic On The Anterior Communicating Artery Complex And The Anterior Communicating Aneurysms

Object: To analyze the hemodynamic characteristics of the anterior communicating artery complex by three-dimensional computer numerical simulation.Materials and Methods: The mean diameter of blood vessels were measured in 23 adults with symmetric A1 segment on CT angiography. ACoAC (anterior communicating artery complex) geometric model had been generated by Gambit 2.3.16 software. In these nine models, The diameter of A1 was fixed in one side, and the other side was decreased by 1/8 d sequently. Then gridded, the mesh were input into the Fluent 6.2.16 software, and the pressure, flow velocity and WSS in different ROIs(Where D-ACoA represents region of ACoA near dominant A1, D-A2 represents region of dominant A2, ND-ACoA represents region of ACoA near non-dominant A1, ND-A2 represents region of non-dominant A2) were calculated. SPSS13.0 was used to perform the statistic analysis. Paired t test was used for analysis of the bilateral symmetric ROIs.Results: With the decrease of the diameter of nondominant A1 segment of the anterior cerebral artery(ACA), The WSS in the region of D-ACoA and ND- ACoA increased, but decreased in the region of D-A2 and ND- A2. The WSS in the region of D-ACoA is great higher than that in the region of ND-ACoA(t=6.543, p<0.05) and significant difference was found between D-A2 and ND- A2 as well(t=6.386, p<0.05). The change of flow velocity was consistent with that of WSS. The pressure in each ROI decreased with the decrease of the diameter of nondominant A1. Conclusions: With the decrease of the diameter of nondominant A1 segment of the ACA, the WSS increases in the ACoA near to dominant A1 segment of the ACA, while the pressure decreases. It is confirmed that WSS may play a very important role in the formation of the anterior communicating aneurysms. Object: To explore the related mechanism of aneurysm growth and rupture by analysis of the hemodynamic characteristics of the anterior communicating aneurysms under the condition of absence of A1 segment of the anterior cerebral artery (ACA) in one side and establishment of three-dimensional computer numerical simulation of aneurysms.Materials and Methods: The mean diameter of blood vessels were measured in 23 adults with symmetric A1 segment on CT angiography. The geometric models had been established by Gambit 2.3.16 software including three groups of anterior communicating aneurysms with absence of the non-dominant A1 segment of the ACA , which the diameter of the neck in the aneurysms were fixed with 1mm, the altitude of the aneurysms were varied from 0.1mm to 0.9mm, the distance between the ACoA aneurysm and the bifurcation in the dominant side was changed from 0.1mm, 0.02mm and 0mm in the three different groups.Then the simulations and hemodynamic parameters, including WSS, velocity of flow, streamline and pressure, were further analyzed by Fluent software.Results: With the growth of the aneurysm, the WSS of cupular part of aneurysm gradually dicreased when the aneurysm locate at 0, 0.1 and 0.02-mm away from the bilateral bifurcates of dominant A1 segment of the ACA under the condition of absence of the non-dominant A1 segment of the ACA,. In models with aneurysm at 0.02mm to the bifurcation, the WSS is lower than 2Pa when the altitude of aneurysms changed from 0.7mm to 0.9mm. In models with aneurysm at the bifurcation, no significant decrease of WSS was found when the altitude of aneurysms changed from 0.6mm to 0.9mm, the mean WSS is lower than 2Pa. In these groups, the nearer the distance between the bilateral bifurcates of dominant A1 segment of the ACA and aneurysm is, the greater the turbulent flow is in the aneurysm. No significant difference of preasure was found in each group with the growth of the aneurysms .Conclusions: When aneurysm in anterior communicating artery grows to some extent, the WSS at cupular part of aneurysm decreases sharply. It suggested that WSS may play an important role in the growth and rupture of the anterior communicating aneurysms. The decrease flow velocity and turbulent flow may contribute to the growth of the aneurysm.