基于MRA的个体化腹主动脉瘤计算机仿真

目的探讨基于MRA图像进行个体化腹主动脉瘤(abdominal aortic aneurysm,AAA)计算机仿真研究的可行性,并从血流动力学层面探讨AAA的发生、发展和破裂机制。方法基于AAA患者的MRA数据采用逆向建模法建立AAA的三维几何模型;采用FLUENT软件进行数值模拟,假设血管壁为刚性壁,血液为不可压缩牛顿流体,建立瞬态模型。将收敛之后的数据导入到CFD-Post中进行结果分析,输出心动周期内不同时刻的血流流线图、流速分布图、血管壁面切应力分布图以及压力分布图。结果AAA瘤颈处血液流动的方式以层流为主,瘤腔内血流以涡流、湍流为主,且在瘤体膨大处较明显;瘤颈处血液流速快于瘤腔,瘤腔大部分区域在整个心动周期内都处于较低的流速水平,且波动不明显,瘤腔内的高流速区域多位于入口血流直接延续的部位;射血期的壁面切应力的量值及其变化幅度均大于充盈期,壁面切应力较高的区域总是分布于瘤颈附近,瘤腔的切应力在整个心动周期内始终处于较低水平;瘤体的壁面压力量值及其分布范围在射血峰值(t=0.08 s)时最大。加速射血期的壁面压力及其变化范围均较减速射血期及充盈期大。结论基于MRA图像可建立个体化的AAA计算机仿真模型,通过计算机仿真得到的AAA内血流分布规律对AAA的研究和临床个体化的诊治有一定的帮助。

Computer simulation of individualized abdominal aortic aneurysm based on MRA

Objective To explore the feasibility of individualized abdominal aortic aneurysm(AAA)computer simulation based on MRA,and to explore the mechanisms of occurrence,progression and rupture of AAA from the perspective of hemodynamics.Methods Based on MRA images of a patient with AAA,the geometric model of AAA was established by reverse modeling method.FLUENT software was used for numerical simulation,assuming that the vascular wall was rigid and the blood was incompressible Newtonian fluid,using transient model.The convergent data were imported into CFD-post software for analysis,outputting the streamline of blood flow,velocity profile of blood flow,wall shear stress profile of AAA and wall pressure profile of AAA at different moments in a cardiac cycle.Results Laminar flow was primary blood flow pattern in AAA’s neck,and eddy flow and turbulent flow were mainly blood flow in AAA’s lumen,especially in the dilated region of AAA.The blood flow velocity in the AAA’s neck fluctuated obviously and was faster than that in the AAA’s lumen.The blood flow velocity of most region of the AAA’s lumen was low throughout the cardiac cycle and hardly fluctuated.The high flow velocity region in AAA’s lumen mostly located in where the inlet blood flow continues directly.The magnitude and variation of wall shear stress in ejection period were greater than those in filling period.The wall shear stress on the AAA’s neck was higher than AAA’s lumen throughout the cardiac cycle,and the latter doesn’t fluctuate much.The wall pressure of the AAA’s body and its distribution maximized when the time of peak ejection(t=0.08 s).The wall pressure and its change range in the accelerated ejection period were larger than those in the decelerated ejection period and filling period.Conclusions A personalized AAA computer simulation based on MRA images can be established and the hemodynamic information in AAA can be obtained,which is of help for AAA’s research and clinical individualized diagnosis and treatment.