Purpose

In a curved vessel such as the aortic arch, the velocity profile closer to the aortic root is normally skewed towards the inner curvature wall, while further downstream along the curve, the velocity profile becomes skewed towards the outer wall. In an aortic dissection (AD) disease, blood velocities in the true lumen (TL) and false lumen (FL) are hypothesized to depend on the proximity of the entry tear to the root of aortic arch. Faster velocity in the FL can lead to higher hemodynamic loading, and pose tearing risk. Furthermore, the luminal velocities control the perfusion rate of radiological contrast media during diagnostic imaging. The objective in this study is to investigate the effect of AD disease morphology and configuration on the blood velocity field in the TL and FL, and on the relative perfusion of radiological enhancement agents through the dissection.

Methods

Eight in vitro models were studied, including patent and non-patent FL configurations. Particle image velocimetry (PIV) was used to quantify the AD velocity field, while laser-induced fluorescence (LIF) was implemented to visualize dynamical flow phenomena and to quantify the perfusion of injected dye, in mimicry of contrast-enhanced computed tomography (CT).

Results

The location of the proximal entry tear along the aortic arch in a patent FL had a dramatic impact on whether the blood velocity was higher in the TL or FL. The luminal velocities were dependent on the entry/reentry tear size combination, with the smaller tear (whether distal or proximal) setting the upper limit on the maximal flow velocity in the FL. Upon merging near the distal reentry tear, the TL/FL velocity differential gave rise to the roll up and shedding of shear layer vortices that convected downstream in close proximity to the wall of the non-dissected aorta. In a non-patent FL, the flow velocity was practically null with all the blood passing through the TL. LIF imaging showed much slower perfusion of contrast dye in the FL compared to the TL. In a patent FL, however, dye had a comparable perfusion rate appearing around the same time as in the TL.

Conclusions

Blood velocities in the TL and FL were highly sensitive to the exact dissection configuration. Geometric case A1R, which had its proximal entry tear located further downstream along the aortic arch, and had its entry and reentry tears sufficiently sized, exhibited the highest FL flow velocity among the tested models, and it was also higher than in the TL, which suggest that this configuration had elevated hemodynamic loading and risk for tearing. In contrast-enhanced diagnostic imaging, a time-delayed acquisition protocol is recommended to improve the detection of suspected cases with a non-patent FL.

中文翻译：

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在专利和非专利主动脉夹层模型中对血流动力学和放射性造影剂灌注的实验性认识。

目的

在诸如主动脉弓之类的弯曲血管中，更靠近主动脉根的速度分布通常偏向内曲率壁，而在沿曲线的更下游处，速度分布偏向外壁。在主动脉夹层（AD）疾病中，假设真管腔（TL）和假管腔（FL）的血流速度取决于进入泪液与主动脉弓根的接近程度。FL中更快的速度可能导致更高的血液动力学负荷，并有撕裂的危险。此外，在诊断成像期间，管腔速度控制放射造影剂的灌注速率。这项研究的目的是研究AD疾病的形态和结构对TL和FL中血流速度场的影响，

方法

研究了八个体外模型，包括专利和非专利FL配置。模仿对比增强计算机断层扫描（CT），使用粒子图像测速（PIV）来量化AD速度场，同时使用激光诱导荧光（LIF）来可视化动态流动现象并量化所注入染料的灌注。 。

结果

专利FL中沿主动脉弓的近端入口撕裂的位置对TL或FL中的血流速度是否较高具有重大影响。腔的速度取决于进入/再进入的眼泪大小的组合，较小的眼泪（无论是远端的还是近端的）设定了FL中最大流速的上限。在远端折返裂口附近合并时，TL / FL速度差引起剪切层涡旋的卷起和脱落，这些剪切层涡旋在紧邻未解剖主动脉壁的下游对流。在非专利FL中，所有血液都通过TL时，流速几乎为零。与TL相比，LIF成像显示FL中对比染料的灌注要慢得多。但是，在专利FL中，

结论

TL和FL中的血流速度对精确的解剖结构高度敏感。几何盒A1R，其近端进入裂口位于主动脉弓的更下游，并且其进入和折返裂口尺寸足够大，在测试模型中表现出最高的FL流速，并且也比TL中的高。提示这种配置具有较高的血液动力学负荷和撕裂风险。在增强对比的诊断成像中，建议使用延时采集协议以改善对非专利FL疑似病例的检测。