Seshadhri Santhosh, Janiga Gábor, Beuing Oliver, Skalej Martin, Thévenin Dominique
Laboratory of Fluid Dynamics and Technical Flows, University of Magdeburg Otto von Guericke, Universitätsplatz 2, D-39106 Magdeburg, Germany.
J Biomech Eng. 2011 Jul;133(7):071005. doi: 10.1115/1.4004410.
Cerebral aneurysms constitute a major medical challenge as treatment options are limited and often associated with high risks. Statistically, up to 3% of patients with a brain aneurysm may suffer from bleeding for each year of life. Eight percent of all strokes are caused by ruptured aneurysms. In order to prevent this rupture, endovascular stenting using so called flow diverters is increasingly being regarded as an alternative to the established coil occlusion method in minimally invasive treatment. Covering the neck of an aneurysm with a flow diverter has the potential to alter the hemodynamics in such a way as to induce thrombosis within the aneurysm sac, stopping its further growth, preventing its rupture and possibly leading to complete resorption. In the present study the influence of different flow diverters is quantified considering idealized patient configurations, with a spherical sidewall aneurysm placed on either a straight or a curved parent vessel. All important hemodynamic parameters (exchange flow rate, velocity, and wall shear stress) are determined in a quantitative and accurate manner using computational fluid dynamics when varying the key geometrical properties of the aneurysm. All simulations are carried out using an incompressible, Newtonian fluid with steady conditions. As a whole, 72 different cases have been considered in this systematic study. In this manner, it becomes possible to compare the efficiency of different stents and flow diverters as a function of wire density and thickness. The results show that the intra-aneurysmal flow velocity, wall shear stress, mean velocity, and vortex topology can be considerably modified thanks to insertion of a suitable implant. Intra-aneurysmal residence time is found to increase rapidly with decreasing stent porosity. Of the three different implants considered in this study, the one with the highest wire density shows the highest increase of intra-aneurysmal residence time for both the straight and the curved parent vessels. The best hemodynamic modifications are always obtained for a small aneurysm diameter.
脑动脉瘤是一项重大的医学挑战，因为治疗选择有限且往往伴随着高风险。从统计学角度来看，患有脑动脉瘤的患者每年有高达3%的人可能会发生出血。所有中风病例中有8%是由动脉瘤破裂引起的。为了防止这种破裂，在微创治疗中，使用所谓的血流导向装置进行血管内支架置入术越来越被视为传统弹簧圈栓塞法的一种替代方案。用血流导向装置覆盖动脉瘤颈部有可能改变血流动力学，从而在动脉瘤腔内诱发血栓形成，阻止其进一步生长，防止其破裂，并可能导致完全吸收。在本研究中，考虑理想化的患者构型，量化不同血流导向装置的影响，其中球形侧壁动脉瘤放置在直的或弯曲的母血管上。当改变动脉瘤的关键几何特性时，使用计算流体动力学以定量和准确的方式确定所有重要的血流动力学参数（交换流速、速度和壁面剪应力）。所有模拟均使用不可压缩的牛顿流体在稳定条件下进行。总体而言，在这项系统研究中考虑了72种不同的情况。通过这种方式，可以根据金属丝密度和厚度比较不同支架和血流导向装置的效率。结果表明，通过插入合适的植入物，可以显著改变动脉瘤内的流速、壁面剪应力、平均速度和涡旋拓扑结构。发现动脉瘤内停留时间随着支架孔隙率的降低而迅速增加。在本研究中考虑的三种不同植入物中，金属丝密度最高的植入物在直的和弯曲的母血管中均显示出动脉瘤内停留时间的最大增加。对于小直径动脉瘤，总是能获得最佳的血流动力学改变。
