Department of Physics and Astronomy, University of Western Ontario, London, ON, Canada.
Med Eng Phys. 2013 Jul;35(7):898-909. doi: 10.1016/j.medengphy.2012.08.020. Epub 2012 Sep 29.
Blood flow instabilities in the carotid artery bifurcation have been highly correlated to clot formation and mobilization resulting in ischemic stroke. In this work, PIV-measured flow velocities in normal and stenosed carotid artery bifurcation models were analyzed by means of proper orthogonal decomposition (POD). Through POD analysis, transition to more complex flow was visualized and quantified for increasing stenosis severity. While no evidence of transitional flow was seen in the normal model, the 50%-stenosed model started to show characteristics of transitional flow, which became highly evident in the 70% model, with greatest manifestation during the systolic phase of the cardiac cycle. By means of a model comparison, we demonstrate two quantitative measures of the flow complexity through the power-law decay slope of the energy spectrum and the global entropy. The more complex flow in the 70%-stenosed model showed a flatter slope of energy decay (-0.91 compared to -1.34 for 50% stenosis) and higher entropy values (0.26 compared to 0.17). Finally, the minimum temporal resolution required for POD analysis of carotid artery flow was found to be 100 Hz when determined through a more typical energy-mode convergence test, as compared to 400 Hz based on global entropy values.
颈动脉分叉处的血流不稳定性与血栓形成和移动密切相关，从而导致缺血性中风。在这项工作中，通过适当的正交分解（POD）分析了正常和狭窄颈动脉分叉模型中的血流速度。通过 POD 分析，可视化并量化了随着狭窄程度的增加向更复杂的血流转变。虽然在正常模型中没有观察到过渡流的证据，但 50%狭窄模型开始表现出过渡流的特征，在 70%模型中变得非常明显，在心脏周期的收缩期表现最为明显。通过模型比较，我们通过能谱的幂律衰减斜率和全局熵来展示两种定量的流复杂性度量。在 70%狭窄模型中，复杂的流动具有更平坦的能量衰减斜率（-0.91 与 50%狭窄时的-1.34 相比）和更高的熵值（0.26 与 0.17 相比）。最后，通过更典型的能量模式收敛测试确定，对颈动脉血流进行 POD 分析所需的最小时间分辨率为 100 Hz，而基于全局熵值则为 400 Hz。
