IEEE Trans Ultrason Ferroelectr Freq Control. 2019 Mar;66(3):493-504. doi: 10.1109/TUFFC.2018.2851846. Epub 2018 Jun 29.
Quantitative ultrasound (QUS) imaging methods, including elastography, echogenicity analysis, and speckle statistical modeling, are available from a single ultrasound (US) radio-frequency data acquisition. Since these US imaging methods provide complementary quantitative tissue information, characterization of carotid artery plaques may gain from their combination. Sixty-six patients with symptomatic ( n = 26 ) and asymptomatic ( n = 40 ) carotid atherosclerotic plaques were included in the study. Of these, 31 underwent magnetic resonance imaging (MRI) to characterize plaque vulnerability and quantify plaque components. US radio-frequency data sequence acquisitions were performed on all patients and were used to compute noninvasive vascular US elastography and other QUS features. Additional QUS features were computed from three types of images: homodyned-K (HK) parametric maps, Nakagami parametric maps, and log-compressed B-mode images. The following six classification tasks were performed: detection of 1) a small area of lipid; 2) a large area of lipid; 3) a large area of calcification; 4) the presence of a ruptured fibrous cap; 5) differentiation of MRI-based classification of nonvulnerable carotid plaques from neovascularized or vulnerable ones; and 6) confirmation of symptomatic versus asymptomatic patients. Feature selection was first applied to reduce the number of QUS parameters to a maximum of three per classification task. A random forest machine learning algorithm was then used to perform classifications. Areas under receiver-operating curves (AUCs) were computed with a bootstrap method. For all tasks, statistically significant higher AUCs were achieved with features based on elastography, HK parametric maps, and B-mode gray levels, when compared to elastography alone or other QUS alone ( ). For detection of a large area of lipid, the combination yielding the highest AUC (0.90, 95% CI 0.80-0.92, ) was based on elastography, HK, and B-mode gray-level features. To detect a large area of calcification, the highest AUC (0.95, 95% CI 0.94-0.96, ) was based on HK and B-mode gray level features. For other tasks, AUCs varied between 0.79 and 0.97. None of the best combinations contained Nakagami features. This study shows the added value of combining different features computed from a single US acquisition with machine learning to characterize carotid artery plaques.
定量超声(QUS)成像方法,包括弹性成像、回声分析和散斑统计建模,可从单个超声(US)射频数据采集获得。由于这些 US 成像方法提供了互补的定量组织信息,因此对颈动脉斑块的特征描述可能会受益于它们的组合。本研究纳入了 66 例有症状(n=26)和无症状(n=40)颈动脉粥样硬化斑块患者。其中 31 例行磁共振成像(MRI)以特征化斑块易损性并定量斑块成分。对所有患者进行 US 射频数据序列采集,并用于计算无创血管 US 弹性成像和其他 QUS 特征。从三种类型的图像中计算出其他 QUS 特征:同相-K(HK)参数图、Nakagami 参数图和对数压缩 B 模式图像。执行了以下六个分类任务:检测 1)小面积脂质;2)大面积脂质;3)大面积钙化;4)破裂的纤维帽;5)基于 MRI 的非易损颈动脉斑块分类与新生或易损斑块的区分;6)症状与无症状患者的确认。首先应用特征选择将 QUS 参数的数量减少到每个分类任务最多三个。然后使用随机森林机器学习算法进行分类。使用 bootstrap 方法计算接收器工作曲线下的面积(AUC)。对于所有任务,与单独使用弹性成像或其他 QUS 相比,基于弹性成像、HK 参数图和 B 模式灰度的特征显著提高了 AUC(<0.001)。对于大面积脂质的检测,获得最高 AUC(0.90,95%CI 0.80-0.92,)的组合基于弹性成像、HK 和 B 模式灰度特征。对于大面积钙化的检测,最高 AUC(0.95,95%CI 0.94-0.96,)基于 HK 和 B 模式灰度特征。对于其他任务,AUC 范围在 0.79 到 0.97 之间。最好的组合中均不包含 Nakagami 特征。本研究表明,结合机器学习使用从单个 US 采集获得的不同特征来对颈动脉斑块进行特征描述具有附加价值。