Institute Biomedical Technology, University of Gent, Ghent, Belgium.
IEEE Trans Ultrason Ferroelectr Freq Control. 2010;57(2):327-39. doi: 10.1109/TUFFC.2010.1413.
Detailed imaging of complex blood flow may improve early diagnosis of cardiovascular disease. In clinical practice, non-invasive flow imaging has been limited to one-dimensional Doppler techniques. Searching for multi-dimensional estimators, research has given attention to speckle tracking (ST) and vector Doppler (VD). However, these techniques have yet to be validated for complex flow patterns as may arise in diseased arteries. In this work, the properties of ST and crossed-beam VD are compared with a ground truth for clinically relevant flow using an ultrasonic simulation environment coupled with the output from computational fluid dynamics (CFD). The statistical properties (n = 80) of ST and VD were first evaluated for stationary flow in a tube for varying vessel positions and angles, and for varying noise levels. The parameter study demonstrated VD to be a more robust axial velocity estimator, and similar results were obtained overall for the lateral velocity component. As an example, the relative standard deviation was 15% and 8% for ST compared with 3% and 10% for VD, for the axial and lateral velocity component, respectively. Further, performance was evaluated for pulsatile flow conditions in a stenosed carotid bifurcation model. A linear regression analysis showed that both methods overall had a good agreement to the CFD reference, however VD suffered from more spurious artifacts and was severely hampered by aliasing in parts of the cardiac cycle. ST was less accurate in estimating the axial component, but prevailed in estimating velocities well beyond the Nyquist range. Based on our simulations, both methods may be used to image complex flow behavior in the carotid bifurcation, however, considering also the scanning limitations of VD, ST may provide a more consistent and practical approach. Future work will entail in vitro and in vivo validation of these results.
详细的血流成像可以提高心血管疾病的早期诊断。在临床实践中，非侵入性的血流成像是有限的一维多普勒技术。为了寻找多维估计器，研究已经关注了斑点跟踪（ST）和向量多普勒（VD）。然而，这些技术尚未在可能出现在患病动脉中的复杂血流模式中得到验证。在这项工作中，斑点跟踪和交叉波束 VD 的特性与使用超声模拟环境与计算流体动力学（CFD）的输出相结合的临床相关流动的真实情况进行了比较。首先，对 ST 和 VD 的统计特性（n=80）在管中进行了固定流动的评估，以研究不同的血管位置和角度以及不同的噪声水平。参数研究表明，VD 是一种更稳健的轴向速度估计器，对于横向速度分量，总体上也得到了类似的结果。例如，与 VD 相比，ST 的相对标准偏差为 15%和 8%，而 VD 的相对标准偏差为 3%和 10%，分别用于轴向和横向速度分量。此外，还对狭窄颈动脉分叉模型中的脉动流条件进行了性能评估。线性回归分析表明，这两种方法总体上与 CFD 参考值具有良好的一致性，但是 VD 容易出现伪影，并且在心脏周期的某些部分受到严重的混叠干扰。ST 在估计轴向分量时不太准确，但在估计超出奈奎斯特范围的速度方面更具优势。根据我们的模拟，这两种方法都可以用于成像颈动脉分叉处的复杂流动行为，但是，考虑到 VD 的扫描限制，ST 可能提供更一致和实用的方法。未来的工作将涉及这些结果的体外和体内验证。
