Roketsan Missile Industries Inc., Elmadag, Ankara 06780, Turkey.
Department of Mechanical Engineering, Middle East Technical University, Ankara 06800, Turkey.
Comput Methods Programs Biomed. 2021 Sep;208:106253. doi: 10.1016/j.cmpb.2021.106253. Epub 2021 Jun 30.
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.
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.
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.
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.
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，使得研究人员能够设计用于动脉狭窄声学检测的新评分系统。本研究通过对狭窄动脉内部血流的数值模拟，了解狭窄严重程度和偏心度对湍流诱导壁压波动和产生声音的影响。
在直径为 6.4 毫米的股动脉模型中生成了五个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。
发现 50%和 60%严重程度的狭窄后湍流活动几乎为零。对于 75%及以上的严重程度，湍流动能显著增加。狭窄出口处管壁上最高湍流活动的位置随着严重程度的增加而降低。95%严重程度模型中看到的最大湍流动能水平比 87%和 75%模型分别高约 9 倍和 31 倍。壁压波动的频谱表明，50%和 60%轴对称模型几乎无声。随着严重程度的增加，频谱开始变得更加丰富，波动强度也随之增加。与轴对称模型相比，50%和 60%偏心模型在 0-150 Hz 频段观察到更多的活动。在它们中，声活动区域的轴向范围也更长。将壁压数据转换为声音表明，对于严重程度为 75%及以上的模型，可获得可视为血管狭窄迹象的杂音。
从模拟结果生成的声音模式与通过多普勒超声获得的典型声音相似，并呈现出明显的特征。结合可以从狭窄动脉内部测量这些声音的传感器技术，可以对其进行处理并用于非侵入性诊断。模拟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，这些数据库可用于训练新的诊断设备。
