不同孔率支架对颅内动脉瘤血流流场影响的计算机模拟研究

Effect of stent with various porosities on blood flow field in intracranial aneurysm:a computer simulation research

目的探讨不同孔率的支架对颅内动脉瘤内血流流场的影响。方法应用三维数值模拟方法，建立窄颈及宽颈两种动脉瘤的三维模型。模拟四种不同孔率（82％、78％、74％及70％）的支架置入载瘤动脉并完全覆盖瘤颈。采用基于计算流体力学（CFD）的软件，计算各种孔率支架置入后，动脉瘤内血流速度、壁面切应力、压力等参数的变化。结果置入82％、78％、74％、70％孔率的支架后，在一个心动周期内，动脉瘤瘤颈远侧壁峰值流速及壁面切应力均随支架孔率的降低而降低；窄颈动脉瘤在一个心动周期内平均流速值分别为0．054、0．036、0．024及0．016m／s，壁面切应力分别为0．529、0．314、0．177及0．122Pa。流速-孔率曲线显示，孔率降至70％左右时，流速随孔率变化趋于平缓；壁面切应力-孔率曲线显示，孔率降至74％左右时，壁面切应力随孔率变化趋于平缓。置入上述4种孔率支架后，宽颈动脉瘤平均流速值依次为0．194、0．178、0．170及0．147m／s；壁面切应力分别为8．466、7．327、7．003及5．744Pa。流速-孔率曲线和壁面切应力-孔率曲线均未显示出速度和壁面切应力随孔率减小趋于平缓的趋势。支架的孔率对窄颈及宽颈动脉瘤瘤颈远侧壁及瘤顶部的压力均无明显影响。结论支架的孔率是影响动脉瘤内血流流场的一个重要参数，随着孔率的降低，动脉瘤内血流速度及壁面切应力相应降低；孔率对动脉瘤内压力没有影响。

To investigate the effect of stent with various porosities on the cerebral aneurysm hemodynamics. Methods The three-dimensional models of narrow and wide-neck aneurysms were established using three-dimensional numerical simulation method, and the aneurysms were situated at the convex walls of blood vessels. Four stent-grafts with different porosity（82%, 78% , 74% and 70% ） were simulated, and they were implanted in parent arteries and covered the aneurysm necks completely. The parameter changes of blood velocity, the wall shear stress and pressure in aneurysms were calculated with computational fluid dynamics （CFD） software after different stent implantations. Results The peak velocity and wall shear stress at distal wall of aneurysm necks were decreased with the reduce of stent porosity in a cardiac cycle after the 82%, 78% , 74% and 70% porosity stents were implanted. The average flow velocity in narrow-neck aneurysms in a cardiac cycle were 0. 054 m/s, 0.036 m/s, 0. 024 m/s, and 0.016 m/s, respectively; the average wall shear stress were 0. 529 Pa, 0. 314 Pa, 0. 177 Pa, and 0. 122 Pa, respectively. The velocity-porosity curve showed that when the porosity was about 70%, the velocity variation tended to moderate. After implanted the stents of 4 porosity, the average flow velocity of the wide-neck aneurysms were 0. 194 m/s, 0. 178 m/s, 0. 170 m/s, and 0. 147 m/s, respectively; the wall shear stress were 8. 466 Pa, 7. 327 Pa, 7. 003 Pa, and 5. 744 Pa, respectively. Both the velocity-porosity eurve and the wall shear stress-porosity curve did not show that the velocity and wall shear stress beeame flat with decreasing of porosity. The stent porosity did not have signifieant impact on the distal wall of aneurysm neck and the pressure at the top of aneurysins. Conclusions The stent porosity is an important parameter of influencing hemodynamics in aneurysm. With the decreasing of the porosity, blood velocity in aneurysms and wall shear stress are relevantly decreased, but have not any influence on the intra-aneurysmal blood pressure.