置入虚拟及真实血流导向装置后兔动脉瘤模型血流动力学的数值模拟研究

Numerical simulation of hemodynamics after virtual and real implanting flow diverters in rabbit aneurysm models

目的 采用计算流体力学（CFD）的方法,研究虚拟血流导向装置（FD）与基于微型CT机重建真实FD对兔动脉瘤血流动力学影响的差异.方法 取新西兰大白兔14只,利用弹性蛋白酶诱导兔右侧颈总动脉瘤模型14个.于造模后3周,行DSA检查重建三维动脉瘤模型,并在载瘤动脉内置入FD.置入FD后3个月处死动物,切取包含FD在内的整段载瘤动脉.用微型CT机扫描所有标本,计算出瘤颈处FD的金属覆盖率（MC）.根据微型CT扫描FD数据,重建真实FD三维模型,运用 Solid Works 软件绘制虚拟三维FD模型.运用计算机软件将真实FD模型和虚拟FD模型分别置入兔动脉瘤三维DSA模型中,并将FD模型与动脉瘤融合.运用CFD的方法,比较虚拟释放FD与真实释放FD对动脉瘤血流动力学影响的差异.结果 ①14个真实FD模型中,MC≥35%组8个,MC〈35%组6个.14个虚拟FD模型的MC为29.4%~31.1%.②在MC≥35%组中,真实FD模型的入射血流量、入射血流速度及归一化的平均壁面切应力（WSS）明显低于虚拟FD模型,相对滞留时间长于虚拟FD模型,差异均有统计学意义,P〈0.05或P〈0.01.壁面压力差异无统计学意义.在MC〈35%组中,真实FD模型与虚拟FD模型各项血流动力学参数差异均无统计学意义.③在真实FD模型中,MC≥35%组的归一化的平均WSS低于MC〈35%组,差异有统计学意义,P＜0.01.在虚拟FD模型中,MC≥35%组与MC〈35%组各项血流动力学参数差异均无统计学意义.结论 基于微型CT重建的真实FD模型,在MC≥35%时,与虚拟FD模型的血流动力学参数有差异.在两种模型的MC接近时,血流动力学参数无差异,提示采用虚拟FD释放技术可用于评估FD置入后血流动力学变化.

Objective To study the differences of the effects of virtual flow diverters （FDs） and mi- cro-CT reconstruction-based real FDs on rabbit aneurysm hemodynamics using the method of computational fluid dynamics （CFD）. Methods Fourteen New Zealand white rabbits were enrolled. Fourteen right common carotid aneurysm models in rabbits were induced by elastase. Three weeks after modeling, DSA examination was performed to rebuild the three-dimensional aneurysm models, and FDs were implanted in aneurysms. Three months after implanting FDs, the rabbits were killed, and a segment of aneurysm, inclu- ding a FD was cut. All specimens were scanned with a micro-CT. The metal coverage （MC） of aneurysm necks was calculated. The real three-dimensional models were rebuilt according to the FD data of micro-CT scan. The virtual three-dimensional FD models were drawn with Solid Works software. The real and virtualFD models were implanted into the three-dimensional DSA models of rabbit aneurysm respectively by using computer softwares, and FD models and aneurysms were fused. The difference of the effects of the virtual and real release FD on aneurysm hemodynamics was compared using the methods of CFD. Results ①Of the 14 real FD models, 8 were in the MC 1〉 35% group and 6 were in the MC 〈 35% group. The MC of 14 virtual FD models was 29.4% to 31.1%. ②In the MC ≥35% group, the inflow volume and the inflow velocity of the real FD models and the mean wall shear stress （WSS） were significantly lower than those in the virtual FD models. The relative retention time was longer than that of the virtual FD models. The differ- ences were statistically significant （ P 〈 O. 05 or P 〈 0.01 ）. There was significant difference in WSS. In the MC 〈35% group, there were no significant differences in all items between the real and virtual FD models. ③In the real FD models, the mean WSS in the MC≥ 35% group was lower than that in the MC 〈 35% group. The difference was statistically significant. In the virtual FD models, there were no signifi- cant differences in all items of hemodynamic parameters between the MC ≥35% group and the MC 〈 35% group. Conclusion Based on the real FD models rebuilt by micro-CT, there is a difference with the he- modynamic parameters of the virtual FD models when MC≥35%. There is no difference in hemodynamic parameters when MC of both the models is near, suggesting that it is feasible for using the virtual FD re- lease technology.