基于流固耦合的颅内动脉瘤破裂的生物力学机制研究

Aassessing the rupture risk of individual intracranial aneurysms and identifying those with higher rupture risk is foremost in aneurysm treatment. Our previous studies have demonstrated that hemodynamics play a major role in the treatment of intracranial aneurysms, which is also the theoretical basis of our independently developed flow diverter (Tubridge). Meanwhile, our recent studies have indicated that the morphological and hemodynamic characteristics were closely related to the rupture of intracranial aneurysms. However, there still exist side by side many problems demanding prompt solution. Among them, the main problem is that those studies were performed by neglecting the difference of wall thickness and mechanical characteristics of aneurysms, while the key problem of aneurysm rupture is imbalance between local hemodynamic stress injury and self-stiffening of aneurysm sac. Thus, in this project, we propose to, 1）measure the wall thicknesses of parent arteries and aneurysms using modern imaging system and gain aneurysm-specific mechanic characteristics of its wall in vitro; 2) analyze the local hemodynamics and aneurysm wall deformation using fluid-structure interaction method in order to explore the correlation between the local hemodynamic stress injury and rupture point of the aneurysm sac; 3) validate the results of CFD analysis using both in vivo (EEG-gated 4D-CTA) and in vitro (microscope observation) methods. This project aims to establish a reliable method to evaluate aneurysm-specific rupture risk while acknowledging the differences of wall thickness and mechanic characteristics of aneurysms, in order to identify those aneurysms with high rupture risk and facilitate clinical decision-making process for unruptured aneurysms.

脑动脉瘤的破裂危险评估分析成为该病防治的关键问题。应用计算流体力学（CFD）技术，我们研究支架对血流动力学的影响，并成功研发新型血流导向装置（Tubridge）。而我们最新研究结果也证实，血流动力学与动脉瘤破裂出血密切相关。但CFD在其破裂研究中仍存在许多问题亟待解决，其中最主要问题是对影响血流动力学的重要因素——瘤壁结构和力学性质进行简单假设；而动脉瘤破裂的核心问题是局部应力损伤与瘤壁自身强度的失平衡。为此，本课题从流体力学与血管壁结构出发：1）利用图像处理系统测量血管及动脉瘤壁厚度，并进行体外应力测试获得个体化的瘤壁力学性质；2）采用流固耦合方法分别计算流体力学和瘤壁形变，比较局部应力损伤与动脉瘤破裂位置的关系；进而以心电图门控的4D-CTA验证瘤壁形变计算结果。本研究从组织结构到流体力学不同层面，分析动脉瘤破裂出血的生物力学机制，为筛查高危的动脉瘤患者并实施尽早干预治疗提供理论依据。

脑动脉瘤的破裂危险评估分析成为该病防治的关键问题。应用计算流体力学（CFD）技术的研究显示血流动力学与动脉瘤破裂出血密切相关。但CFD在其破裂研究中仍存在许多问题亟待解决，其中最主要问题是对影响血流动力学的重要因素——瘤壁结构和力学性质进行简单假设；而动脉瘤破裂的核心问题是局部应力损伤与瘤壁自身强度的失平衡。为此，本课题从流体力学与血管壁结构出发：1）构建兔的动脉瘤模型，并对其瘤壁结构进行病理组织学分析；2）应用3.0T 磁共振对囊性动脉瘤的管壁扫描成像，比较瘤壁强化的危险因素，结果显示动脉瘤大小（OR=3.727，95%CI：1.993～6.971，P＜0.01、不规则形态（OR=3.990，95%CI：1.219～13.065，P=0.0 22）为动脉瘤瘤壁强化的独立危险因素，提示动脉瘤大小和不规则形态与瘤壁异常强化密切相关。。此外应用PHASES对动脉瘤破裂风险进行评价，并与瘤壁强化程度进行相关性，多因素分析结果显示动脉瘤最大径 （OR=1.536，95%CI：1.312~1.798）、部位（OR=1.592，95%CI：1.237~2.049）为瘤壁 强化的独立危险因素。3）建立病例特异性的脑动脉瘤模型，并进行计算流体力学（CFD）分析：根据瘤壁强化程度不同，分为无强化组（39例）、部分强化组（14例）和环形强化组（12例），单因素分析提示平均壁面切应力（NWSS）、最小壁面切应力（min WSS）和LSA、RRT三组间存在显著差异。logistic回归分析NWSS瘤壁强化的独立危险因素，提示血流动力学与动脉瘤强化及破裂风险相关。4）完成29例动脉瘤的心电门控4D-CTA扫描，结果显示心动周期内出现明显瘤体形变的动脉瘤站62.1%，无明显变化37.9%。本研究从组织结构到流体力学不同层面，分析动脉瘤破裂出血的生物力学机制，为筛查高危的动脉瘤患者并实施尽早干预治疗提供理论依据。