【作者】 鲁刚；

【导师】 耿道颖；

【作者基本信息】 复旦大学 ， 影像医学与核医学， 2011， 博士

【副题名】基于患者的3D计算机模拟

【摘要】 第一部分病人特征性颅内动脉瘤三维血流动力学刚性壁模型的建立及探讨目的：通过病人CTA或3D-DSA数据,建立病人特异性三维血流动力学刚性壁模型,应用计算流体力学的方法分析模型的血流动力学特征参数,并对可能对模型计算结果产生影响的因素,包括网格密度、流体的特性及模型合适的载瘤动脉截取方法进行探讨,确定合适的模型建立条件,使得计算结果稳定可靠。材料方法：选取2例颅内动脉瘤患者,通过CTA或3D-DSA数据,重建动脉瘤几何模型,然后利用商用CFD软件ANSYS CFX 12.0,并使用有限元方法进行数值模拟。再次分别选取1-2例颅内动脉瘤进行模型重建,计算并比较不同网格划分(按照网格最大径的不同划分),不同流体特性(牛顿流体和非牛顿流体),以及不同模型截取方法(载瘤动脉不同的保留方式)对动脉瘤流场的影响。结果：建立2例颅内动脉瘤的三维模型并进行数值模拟,计算模型的血流流速、流线、WSS等血流动力学特征参数。不同网格密度划分对动脉瘤血流动力学存在显著的影响,随网格密度的增大,平均WSS增大,在0.4 mm-0.25 mm网格直径模型,网格最大径每下降0.05mm, WSS相应变化约8%-15%,0.25 mm-0.15 mm网格直径之内的模型,WSS变化均在5%以内。牛顿流体及非牛顿流体模型下,模型的流线及瘤颈部位的流速差别很小,在心脏收缩末期WSS及整个心动周期内平均WSS差别也较小,最大约相差3.59%。入口截取过短,会低估动脉瘤区域流线的复杂程度,动脉瘤冲击范围减小,流速减慢,同时导致冲击区域WSS估计错误；出口对模型的流线、WSS等血流动力学参数影响较小。结论：通过建立病人特异性三维血流动力学刚性壁模型,可以获得动脉瘤的血流动力学特征参数,为研究动脉瘤的生长、破裂等的血流动力学因素提供了良好的平台。CTA及3D-DSA图像,通过第三方软件均可以建立三维动脉瘤模型,3D-DSA重建的模型分辨率更高,模型简化、光滑化等处理更容易,但CTA可一次重建全脑血管,对于存在双侧供血动脉的动脉瘤,如前交通动脉瘤及基底动脉瘤,CTA是更好的选择。不同的网格密度,对CFD计算结果产生明显的影响,颅内动脉瘤模型,选用的网格最大径应小于0.25mm,以保证计算结果的稳定性。牛顿流体及非牛顿流体对模型内的流场状态影响很小,因此使用牛顿流体代替非牛顿流体进行CFD的数值模拟,结果是可信的。模型载瘤动脉的不同截取方法可能对CFD的模拟结果产生明显的影响,因此在建立模型时,应考虑如何正确的截取模型,入口处应位于载瘤动脉直管段,且不可距离动脉瘤过近,入口段载瘤动脉至动脉瘤应保留足够的长度,保证血流在其中能充分发展。出口保留的长度对动脉瘤模型的影响较小第二部分颅内破裂动脉瘤与非破裂动脉瘤血流动力学配对参数比较目的：三维重建发生破裂的颅内镜像动脉瘤,利用计算流体力学方法进行模拟,研究与颅内破裂动脉瘤相关的血流动力学因素。材料方法：旋转DSA诊断的9例镜像动脉瘤患者,每例患者均分为破裂组动脉瘤及非破裂组动脉瘤,计算WSS及OSI等血流动力学参数并进行比较。结果：心脏手术末期,动脉瘤区域平均WSS与载瘤动脉平均WSS,在破裂组中,有明显的差别,8.78±3.57PaVS6.49±3.48pa(P=0.015),非破裂在中差别无统计学意义,9.80±4.12Pa VS10.17±7.48pa(P=0.678)。破裂组动脉瘤,平均地WSS范围为12.20±18.08%,非破裂组为3.96±6.91%,两组差异有统计学意义(P=0.015)。破裂组的动脉瘤区域平均的震荡因子(OSI)为0.0879±0.0764,未破裂组为0.0183±0.0191,破裂组明显高于非破裂组(P=0.008)。结论：镜像动脉瘤是一个非常有效的动脉瘤疾病模型,可用于研究与动脉瘤破裂相关的血流动力学因素。破裂动脉瘤表面平均WSS较低,具有更大范围的低WSS区域,同时OSI明显高于非破裂组动脉瘤。第三部分病人特征性颅内动脉瘤三维血流动力学弹性壁模型的建立及初步探讨目的：通过病人3D-DSA数据,建立病人特征性颅内动脉瘤三维血流动力学弹性壁模型,应用计算流体力学的方法分析模型的血流动力学特征参数,并分析不同弹性模量对动脉瘤血流动力的影响。材料方法：选取1例颅内动脉瘤患者,通过3D-DSA重建动脉瘤几何模型,然后利用商用CFD软件ANSYS Workbench12.0及CFX 12.0,使用有限元方法进行流固耦合模拟。再次选取2例颅内动脉瘤分别建立动脉瘤弹性壁模型(按照假设动脉瘤弹性模量的不同E=2MPa、10MPa、40MPa分别建立)及刚性壁模型,然后利用商用CFD软件ANSYS Workbench 12.0及CFX 12.0,并使用有限元方法进行数值模拟,比较不同弹性模量模型间及与刚性壁模型的血流动力学参数差异。结果：建立颅内动脉瘤的三维弹性壁模型并进行数值模拟,并模拟了血管壁及血流特征性参数,包括血管壁Von Mises应力、变形,血管腔内的流场。模型中变形最大的区域位于动脉瘤体部,动脉瘤高应力区域集中分布在动脉瘤瘤颈部。对弹性壁模型间比较及与刚性壁模型的比较研究结果显示随着弹性模量的增大,模型变形减小,模型中弹性壁对WSS分布及大小影响有限,刚性壁模型与2MPa弹性壁模型平均WSS相差<5%。结论：初步建立病人特征性颅内动脉瘤三维血流动力学弹性壁模型,并进行血流动力学参数分析。血管壁的变形与模型的几何形状相关。弹性壁模型对动脉瘤颈部的流速分布,可能产生明显的影响,随着弹性模量的增大,瘤颈部的冲击区域逐渐减小,而冲击域的血流流速则可见加快,因此刚性壁模型可能高估动脉瘤破裂的风险。弹性壁对动脉壁WSS分布影响较小。更多还原

【Abstract】 PartⅠEstablishment of patient-specific intracranial aiieurysm 3D rigid wall CFD modelObjective Through 3D-DSA and CTA data, a patient-specific intracranial aneurysms rigid wall CFD model was established to analyze aneurysm hemodynamic characteristics. Investigate the possible factors; include grid density, the fluid characteristics and appropriate interception of the parent artery, which may affect the results. Determine the appropriate conditions to reconstracte the model. Methods Two cases of intracranial aneurysms diagnosed by 3D-DSA or CTA were reconstructed. The commercial CFD software ANSYS CFX 12.0 and finite element method to numerical simulate was used. Select 1-2 cases of intracranial aneurysm to simulate and compared the influence of different grid density, fluid characteristics and parent artery interception methods to the aneurysms flow field. Results Two cases of intracranial aneurysm model were simulated and the flow velocity, flow lines, WSS of the model was calculated. Different grid density had great effect on aneurysm hemodynamics factors. With the increase of grid density, the average WSS increased too. When the maximum diameter of grid was within 0.4mm-0.25mm, the size of grid decreased about 0.05mm and WSS raised 8%-15%. If the size of grid was smaller than 0.25mm, the change of WSS was less than 5%. The differences of streamline and flow velocity between Newtonian and non-Newtonian fluid model were very minor. The biggest difference of the average WSS in a whole cardiac cycle was only about 3.59%. If the inlet interception was presetted too short, the complexity of the flow streamlines in aneurysm region would be underestimated, reduce the scope of the impact of aneurysm, and the flow rate slowed down, which leads to miscalculate the WSS in the impact ion zone. The outlet interception has little impact to the model hemodynamics parameters, such as streamlines, WSS distribution. Conclusion Patient-specific 3-D computational fluid dynamic model of intracranial aneurysm can show the hemodynamic features of the parent artery and aneurysms, which can be used to further analysis hemodynamic. The model reconstruction by 3D-DSA has higher resolution and easier to simplified, and smooth. CTA can reconstruct of whole cerebral blood vessels in one check. For the existence of bilateral artery aneurysms, such as the anterior communicating artery (ACom artery) and the basilar artery aneurysm, CTA is the better choice. The different sizes of the grid have significant influences on the intracranial aneurysms hemodynamic. In intracranial aneurysm model, ino rder to ensure the stability of the results, the grid size should be less than 0.25mm. Newtonian and non-Newtonian fluids have little effect on the intracranial aneurysm flow field, so instead of non-Newtonian fluid, using Newtonian fluid to simulate the aneurysms hemodynamic is reliable. The parent artery interception methods may affect the CFD results singnificently; modeling should consider how to correct the interception model. The inlet of the model should locate in the straight sections of the parent artery. The inlet to the aneurysm should be of sufficient length to ensure blood flow would fully development in the parent artery. The retention of outlet have little impact to the CFD model.PartⅡComparison of hemodynamics factors between ruptureand and unrupture intracranial aneurysms.Objective To investigate the impacts of hemodynamic factors on rupture of mirror intracranial aneurysms with 3D reconstruction model computational fluid dynamic (CFD) simulation. Methods Rotation digital subtraction angiography (RDSA) was performed in nine pairs of mirror aneurysms (MANs). Each pair was divided into two groups, the ruptured group and unruptured group. The hemodynamic factors of parent arteries and aneurysms were compared. Results There was significant difference between wall shear stress (WSS) spatially averaged at peak systole of parent artery and average WSS of aneurysm region in the reptured group, i.e,8.78±3.57Pa VS 6.49±3.48pa (P=0.015), but not significant difference in the unruptured group, i.e,9.80±4.12Pa VS 10.17±7.48pa (P=0.678). The average proportion of low WSS area to whole area of aneurysm was 12.20±18.08% in the ruptured group VS 3.96±6.91% in the unruptured group, the difference between them was statistical significance (P=0.015). Average oscillatory shear index (OSI) was 0.0879±0.0764 in the ruptured group, which is significantly higher than that of the unruptured group, i. e,0.0183±0.0191 (P=0.008). Conclusions MANs may be a useful disease model to investigate possible reasons linked to ruptured aneurysms. The ruptured group manifested wider range of low WSS, higher proportion of low WSS area to whole area of aneurysm and higher OSI compared with the unruptured group.PartⅢEstablishment of patient-specific intracranial aneurysm 3D FSI CFD modelObjective A 3D transient fluid-solid coupling model of the blood flow in arteries has been developed in order to study the influence of fluid solid interaction on intracranial aneurysm. Methods A case of intracranial aneurysm was reconstracted by 3D-DSA. The commercial CFD software ANSYS Workbench 12.0, CFX 12.0 and finite element method to numerical simulate was used to FSI. Blood is assumed to be incompressible, Newtonian fluid and laminar flow in the patient-specific intracranial aneurysm. Two cases were selected to established FSI model(assuming the different arterial elastic modulus E=2MPa, 10MPa,40MPa) and rigid wall model. ANSYS Workbench 12.0, CFX 12.0, and FEA was used to simulate, then the differences of hemodynamic parameters between various elastic modulus models and rigid wall model were compared. Results The 3-dimensional elastic aneurysm wall model was created and simulation was performed. The artery wall and fluid field parameters were calculated, such as the vessel wall, Von Mises stress, deformation, flow field. In the model, the largest deformation regional was in the meddle of aneurysms, and high stress concentrated in areas of aneurysm neck. The difference between various elastic modulus models and rigid wall modelshow with the elastic modulus increases, the model deformation decreases, and elastic wall modelhas limited impact to the WSS distribution. The difference average WSS between rigid wall model and the elastic wall (E=2MPa) was less than 5%. Conclusions Patient-specific intracranial aneurysm 3D FSI model was initial establishment and the hemodynamic paratemers were calculated. Deformation of the vascular wall associated with the model geometry. Elastic wall model may have significant impact in the velocity distribution of aneurysm neck. Rigid wall model may overestimate the risk of aneurysm rupture. Elastic wall model have less impact the WSS distribution in the arterial wall.更多还原