Background and objectives

Recent developments of low-cost, compact acoustic sensors, advanced signal processing tools and powerful computational resources allow researchers design new scoring systems for acoustic detection of arterial stenoses. In this study, numerical simulations of blood flow inside stenosed arteries are performed to understand the effect of stenosis severity and eccentricity on the turbulence induced wall pressure fluctuations and the generated sound.

Methods

Axisymmetric and eccentric elliptic stenoses of five different severities are generated inside a 6.4 mm diameter femoral artery model. Large eddy simulations of pulsatile, non-Newtonian blood flow are performed using the open source software OpenFOAM.

Results

Post-stenotic turbulence activity is found to be almost zero for 50 and 60% severities. For severities of 75% and more, turbulent kinetic energy rises significantly with increasing severity. The location of the highest turbulence activity on the vessel wall from the stenosis exit decreases with increasing severity. The maximum level of turbulent kinetic energy seen in 95% severity models is about 9 and 31 times higher than that of 87% and 75% models, respectively. Spectrum of wall pressure fluctuations show that 50 and 60% axisymmetric models are almost silent. The spectrum starts to get richer with 75% severity, and the fluctuation intensity increases with severity. Compared to the axisymmetric models, more activity is observed in the 0–150 Hz band for the 50 and 60% eccentric models. Axial extent of the acoustically active region is also longer in them. Converting wall pressure data into sound revealed that murmurs that can be considered as signs of vascular stenosis are obtained for models with 75% and higher severity.

Conclusions

Sound patterns generated from simulation results are similar to the typical sounds obtained by Doppler ultrasonography, and present distinct characters. Together with a sensor technology that can measure these sounds from within the stenosed artery, they can be processed and used for the purpose of non-invasive diagnosis. Computational fluid dynamics studies that simulate large number of cases with different stenosis severities and morphologies will play a critical role in developing the necessary sound databases, which can be used to train new diagnostic devices.

中文翻译：

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不同严重程度和偏心率的狭窄股动脉模型内湍流诱导的声音生成模拟

背景和目标

低成本、紧凑的声学传感器、先进的信号处理工具和强大的计算资源的最新发展使研究人员能够设计新的评分系统，用于动脉狭窄的声学检测。在这项研究中，对狭窄动脉内的血流进行了数值模拟，以了解狭窄严重程度和离心率对湍流引起的壁压波动和产生的声音的影响。

方法

在 6.4 毫米直径的股动脉模型内生成了五种不同严重程度的轴对称和偏心椭圆形狭窄。使用开源软件 OpenFOAM 对脉动、非牛顿血流进行大涡模拟。

结果

发现狭窄后湍流活动对于 50% 和 60% 的严重程度几乎为零。对于 75% 或更高的严重程度，湍流动能随着严重程度的增加而显着增加。来自狭窄出口的血管壁上最高湍流活动的位置随着严重程度的增加而减少。在 95% 严重程度模型中看到的最大湍流动能水平分别比 87% 和 75% 模型高出约 9 倍和 31 倍。壁面压力波动的频谱显示，50% 和 60% 的轴对称模型几乎是无声的。75% 严重程度时频谱开始变得更丰富，波动强度随着严重程度而增加。与轴对称模型相比，50% 和 60% 偏心模型在 0-150 Hz 波段观察到更多的活动。在它们中声学有效区域的轴向范围也更长。将壁压数据转换为声音显示，对于严重程度为 75% 或更高的模型，会出现可被视为血管狭窄迹象的杂音。

结论

模拟结果产生的声音模式与多普勒超声获得的典型声音相似，具有鲜明的特征。结合可以从狭窄动脉内测量这些声音的传感器技术，它们可以被处理并用于非侵入性诊断的目的。模拟具有不同狭窄严重程度和形态的大量病例的计算流体动力学研究将在开发必要的声音数据库方面发挥关键作用，可用于训练新的诊断设备。