Purpose

There has been interest in recent work in using computational fluid dynamics with Lagrangian analysis to calculate the trajectory of emboli-like particles in the vasculature. While previous studies have provided an understanding of the hemodynamic factors determining the fates of such particles and their relationship to risk of stroke, most analyses have relied on a particle equation of motion that assumes the particle is “small” e.g., much less than the diameter of the vessel. This work quantifies the limit when a particle can no longer be considered “small”.

Methods

The motion of embolus-like particles are simulated using an overset mesh technique. This allows the fluid stresses on the particle surface to be fully resolved. Consequently, the particles can be of arbitrary size or shape. The trajectory of resolved particles and “small” particles are simulated through a patient-specific carotid artery bifurcation model with particles 500, 1000, and 2000 μm in diameter. The proportions of particles entering the internal carotid artery are treated as the outcome of the particle fate, and statistical comparisons are made to ascertain the importance of non-small particle effects.

Results

For the 2000 μm embolus, the proportion of particles traveling to the internal carotid artery is 74.7 ± 1.3% (mean ± 95% confidence margin) for the “small” particle model and is 85.7 ± 5.4% for a resolved particle model. The difference is statistically significant, \(p< 0.05\), based on the binomial test for the particle outcomes. No statistically discernible differences are found for the smaller diameter particles.

Conclusions

Quantitative differences are observable for the 2000 μm trajectories between the “small” and resolved particle models which is a particle diameter 27% relative to the common carotid artery diameter. A fully resolved particle model ought to be considered for emboli trajectory simulations when the particle size ratio is ≳ 20%.

中文翻译：

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具有完全解析的粒子表面的栓子传输模拟。

目的

在最近的工作中，使用拉格朗日分析法中的计算流体动力学来计算脉管系统中栓塞样颗粒的轨迹已经引起了人们的兴趣。尽管先前的研究已经了解了确定此类颗粒命运的血流动力学因素及其与中风风险之间的关系，但大多数分析还是基于颗粒的运动方程，该方程假定颗粒“很小”，例如远小于直径。的船只。当不再可以将粒子视为“小”时，这项工作量化了极限。

方法

栓子样颗粒的运动是使用过度网格技术进行模拟的。这使得颗粒表面上的流体应力得以完全消除。因此，颗粒可以具有任意大小或形状。解决颗粒和“小”粒子的轨迹是通过与颗粒500，1000患者特异性颈动脉分叉模型模拟，2000  μ直径米。进入颈内动脉的颗粒比例被视为颗粒结局的结果，并进行统计比较以确定非小颗粒效应的重要性。

结果

为2000年 μ米栓子，行进到颈内动脉的颗粒的比例为“小”粒子模型74.7±1.3％（平均值±95％置信余量）和为解决粒子模型85.7±5.4％。基于对粒子结果的二项式检验，差异具有统计学显着性，\（p <0.05 \）。对于较小直径的颗粒，没有发现统计学上可辨别的差异。

结论

量的差异是可观察到的为2000年 μ “小”和解决粒子模型粒径相对于颈总动脉直径的27％，这是米之间的轨迹。当粒径比为≳20％时，应考虑使用完全解析的颗粒模型进行栓子轨迹模拟。