Li Ronny X, Apostolakis Iason Z, Kemper Paul, McGarry Matthew D J, Ip Ada, Connolly Edward S, McKinsey James F, Konofagou Elisa E
Ultrasound and Elasticity Imaging Laboratory, Department of Biomedical Engineering, Columbia University, New York, New York, USA.
Department of Neurologic Surgery, New York-Presbyterian Hospital/Columbia University Medical Center, New York, New York, USA.
Ultrasound Med Biol. 2019 Feb;45(2):353-366. doi: 10.1016/j.ultrasmedbio.2018.07.013. Epub 2018 Nov 12.
Carotid stenosis involves narrowing of the lumen in the carotid artery potentially leading to a stroke, which is the third leading cause of death in the United States. Several recent investigations have found that plaque structure and composition may represent a more direct biomarker of plaque rupture risk compared with the degree of stenosis. In this study, pulse wave imaging was applied in 111 (n = 11, N = 13 plaques) patients diagnosed with moderate (>50%) to severe (>80%) carotid artery stenosis to investigate the feasibility of characterizing plaque properties based on the pulse wave-induced arterial wall dynamics captured by pulse wave imaging. Five (n = 5 patients, N = 20 measurements) healthy volunteers were also imaged as a control group. Both conventional and high-frame-rate plane wave radiofrequency imaging sequences were used to generate piecewise maps of the pulse wave velocity (PWV) at a single depth along stenotic carotid segments, as well as intra-plaque PWV mapping at multiple depths. Intra-plaque cumulative displacement and strain maps were also calculated for each plaque region. The Bramwell-Hill equation was used to estimate the compliance of the plaque regions based on the PWV and diameter. Qualitatively, wave convergence, elevated PWV and decreased cumulative displacement around and/or within regions of atherosclerotic plaque were observed and may serve as biomarkers for plaque characterization. Intra-plaque mapping revealed the potential to capture wave reflections between calcified inclusions and differentiate stable (i.e., calcified) from vulnerable (i.e., lipid) plaque components based on the intra-plaque PWV and cumulative strain. Quantitatively, one-way analysis of variance indicated that the pulse wave-induced cumulative strain was significantly lower (p < 0.01) in the moderately and severely calcified plaques compared with the normal controls. As expected, compliance was also significantly lower in the severely calcified plaques regions compared with the normal controls (p < 0.01). The results from this pilot study indicated the potential of pulse wave imaging coupled with strain imaging to differentiate plaques of varying stiffness, location and composition. Such findings may serve as valuable information to compensate for the limitations of currently used methods for the assessment of stroke risk.
颈动脉狭窄是指颈动脉管腔变窄，这有可能导致中风，而中风是美国第三大死因。最近的几项研究发现，与狭窄程度相比，斑块结构和成分可能是更直接的斑块破裂风险生物标志物。在本研究中，对111名（n = 11，N = 13个斑块）被诊断为中度（>50%）至重度（>80%）颈动脉狭窄的患者应用脉搏波成像，以研究基于脉搏波成像捕获的脉搏波诱导动脉壁动力学来表征斑块特性的可行性。还对5名（n = 5名患者，N = 20次测量）健康志愿者进行成像作为对照组。使用传统和高帧率平面波射频成像序列在狭窄颈动脉段的单个深度生成脉搏波速度（PWV）的分段图，以及在多个深度进行斑块内PWV映射。还为每个斑块区域计算斑块内累积位移和应变图。基于PWV和直径，使用布拉姆韦尔 - 希尔方程估计斑块区域的顺应性。定性地，观察到动脉粥样硬化斑块区域周围和/或内部的波汇聚、PWV升高和累积位移降低，这些可能作为斑块表征的生物标志物。斑块内映射显示有潜力捕获钙化内含物之间的波反射，并基于斑块内PWV和累积应变区分稳定（即钙化）和易损（即脂质）斑块成分。定量分析方面，单因素方差分析表明，中度和重度钙化斑块中的脉搏波诱导累积应变显著低于正常对照组（p < 0.01）。正如预期的那样，重度钙化斑块区域的顺应性也显著低于正常对照组（p < 0.01）。这项初步研究的结果表明，脉搏波成像结合应变成像有可能区分不同硬度、位置和成分的斑块。这些发现可能是有价值的信息，以弥补当前用于评估中风风险方法的局限性。
