基于有限元方法的颅内夹层动脉瘤的分层扩展机理研究

Intracranial dissecting aneurysm is one of the most complex and most dangerous vascular diseases, but few studies concerned with the mechanism of delamination propagation. Taking intracranial arteries as study objects, delamination failure mechanisms with viscoelastic behavior will be proceed: Firstly, Taking arterial specimens with different directions to the axial of aorta and different layers as research objects, then stress-relaxation and uniaxial tension tests are carried out to obtain the constitutive parameters through inverse analysis of these tests based on the constitutive model with consideration of the viscoelastic behavior of the constructions under micro-scale. Through the comparison of the finite element analysis results and the outcomes from analysis with Digital correlation method in order to verify the viscoelastic constitutive model. Secondly, taking the specimens from uniaxial tension tests as research objects and the delamination tests under different fracture modes are carried out in order to acquire the fracture parameter-energy release rate. Through the comparison of the finite element analysis between experimental measurement with the delamination process under different fracture modes, the verifications of the fracture model are performed. Moreover, the relations between the stress-strain and propagation direction of the delamination front are analyzed. Finally, through the finite element analysis of the delamination propagation of the three-dimensional ideal model of the dissection aneurysm and the analysis of the three-dimensional model of the patients, the delamination expansion prediction analysis was carried out. In a word, the execution of this project can construct the theoretical system of delamination and failure of intracranial arterial layers which considering the viscoelastic effect and found the bases of prediction of delamination propagation of intracranial dissecting aneurysm as well as the simulation prediction of vascular interventional treatment.

颅内夹层动脉瘤是最复杂、最危险的血管疾病之一，然而其分层扩展的机理研究甚少。本项目采用颅内动脉血管进行粘弹性和分层扩展研究：首先，对沿血管轴线不同角度和不同层的动脉血管壁试样开展应力松弛和单向拉伸实验，并通过建立考虑血管微观结构的粘弹性本构模型的有限元的自动逆分析程序，获得其本构模型参数。通过有限元分析和数字图像相关技术得到血管壁在单向拉伸过程中力学特性的对比，验证此模型的正确性；其次，对单向拉伸实验的试样进行各种断裂模式的分层断裂扩展实验以获得断裂参数-能量释放率。通过有限元分析验证断裂模型的正确性以及分析裂纹前沿应力应变与扩展方向的关系；最后，通过有限元对夹层动脉瘤三维理想模型的分层扩展进行参数化分析以及对患者的三维模型进行分层扩展损伤分析。本项目的实施能建立考虑粘弹性效应的颅内动脉血管壁分层损伤断裂的理论体系，为颅内夹层动脉瘤的分层扩展预测和血管介入治疗仿真预测打下基础。

动脉血管的分层是由内层的破裂或者内层穿孔时出血和血肿的形成造成的，并且在主动脉或者颅内动脉分支的位置都会出现。颅内动脉夹层动脉瘤占所有颅内动脉瘤的12%左右。颅内夹层动脉瘤常常引发起蛛网膜下腔出血、缺血性脑卒中等相关的脑血管并发症。流行病学研究表明，在中国，颅内动脉夹层动脉瘤年发病率大约4~6/100000，可发病于任何年龄阶段，无显著性别差异，高发年龄在 50 岁左右，其临床表现复杂多样、误诊率和病死率高，是最复杂和危险的血管疾病之一。本研究基于实测应力松弛响应和单轴拉伸试验结合数字图像相关技术，建立了考虑血管不同微观组织结构的动脉壁粘弹性本构模型，并且通过反演算方法得到了材料参数。为了确定人体血管组织的粘合界面的参数值，开发并演示了一种基于反分析方法和一种基于有限元的模拟人体血管纤维帽撕裂事件的建模方法。采用HGO模型和CZM模型对人体血管纤维帽的撕裂行为进行了仿真研究。通过对人体血管纤维帽的单轴拉伸试验进行逆建模，获得HGO参数值，并作为本体材料模型的输入值，模拟纤维帽撕裂过程。采用相同的反分析方法，定量计算了纤维帽厚度范围内的粘结界面强度和临界能量释放速率，揭示了人体血管纤维帽的撕裂分层扩展机理。通过前面的血管材料参数和血管力学仿真模拟的基础，进行了大量的颅内夹层动脉瘤和囊状动脉瘤的破裂的仿真分析和手术预案的仿真分析。相关的仿真分析模型已经成功应用于颅内动脉瘤的手术预案分析和结构性心脏病的心脏瓣膜支架的预案仿真分析中；其中的颅内动脉瘤手术预案已经形成了临床中动脉瘤治疗的方案选择和治疗后的预后分析的重要手段，完成了5篇的动脉瘤手术治疗后的结果分析的SCI文章；心脏瓣膜的仿真分析目前已经完成了整个计算分析的流程。