IEEE Trans Ultrason Ferroelectr Freq Control. 2016 Oct;63(10):1613-1623. doi: 10.1109/TUFFC.2016.2572260. Epub 2016 May 26.
Cardiovascular disease (CVD) is a leading cause of death and is in the majority of cases due to the formation of atherosclerotic plaques in arteries. Initially, thickening of the inner layer of the arterial wall occurs. Continuation of this process leads to plaque formation. The risk of a plaque to rupture and thus to induce an ischemic event is directly related to its composition. Consequently, characterization of the plaque composition and its proneness to rupture are of crucial importance for risk assessment and treatment strategies. The carotid is an excellent artery to be imaged with ultrasound because of its superficial position. In this review, ultrasound-based methods for characterizing the mechanical properties of the carotid wall and atherosclerotic plaque are discussed. Using conventional echography, the intima media thickness (IMT) can be quantified. There is a wealth of studies describing the relation between IMT and the risk for myocardial infarction and stroke. Also the carotid distensibility can be quantified with ultrasound, providing a surrogate marker for the cross-sectional mechanical properties. Although all these parameters are associated with CVD, they do not easily translate to individual patient risk. Another technique is pulse wave velocity (PWV) assessment, which measures the propagation of the pressure pulse over the arterial bed. PWV has proven to be a marker for global arterial stiffness. Recently, an ultrasound-based method to estimate the local PWV has been introduced, but the clinical effectiveness still needs to be established. Other techniques focus on characterization of plaques. With ultrasound elastography, the strain in the plaque due to the pulsatile pressure can be quantified. This technique was initially developed using intravascular catheters to image coronaries, but recently noninvasive methods were successfully developed. A high correlation between the measured strain and the risk for rupture was established. Acoustic radiation force impulse (ARFI) imaging also provides characterization of local plaque components based on mechanical properties. However, both elastography and ARFI provide an indirect measure of the elastic modulus of tissue. With shear wave imaging, the elastic modulus can be quantified, although the carotid artery is one of the most challenging tissues for this technique due to its size and geometry. Prospective studies still have to establish the predictive value of these techniques for the individual patient. Validation of ultrasound-based mechanical characterization of arteries and plaques remains challenging. Magnetic resonance imaging is often used as the "gold" standard for plaque characterization, but its limited resolution renders only global characterization of the plaque. CT provides information on the vascular tree, the degree of stenosis, and the presence of calcified plaque, while soft plaque characterization remains limited. Histology still is the gold standard, but is available only if tissue is excised. In conclusion, elastographic ultrasound techniques are well suited to characterize the different stages of vascular disease.
心血管疾病 (CVD) 是导致死亡的主要原因,大多数情况下是由于动脉中动脉粥样硬化斑块的形成。最初,动脉壁内层变厚。如果这个过程继续下去,就会导致斑块的形成。斑块破裂并因此引发缺血性事件的风险与斑块的组成直接相关。因此,对斑块的组成及其易破裂程度进行特征描述对于风险评估和治疗策略至关重要。由于颈动脉的位置较浅,因此是进行超声成像的极佳动脉。在本综述中,讨论了基于超声的方法来描述颈动脉壁和动脉粥样硬化斑块的机械特性。使用传统的超声检查,可以定量测量内膜中层厚度 (IMT)。有大量研究描述了 IMT 与心肌梗死和中风风险之间的关系。还可以使用超声测量颈动脉顺应性,为横截面的机械特性提供替代标志物。尽管所有这些参数都与 CVD 相关,但它们并不能轻易转化为个体患者的风险。另一种技术是脉搏波速度 (PWV) 评估,它测量动脉床上压力脉冲的传播。PWV 已被证明是全身动脉僵硬度的标志物。最近,引入了一种基于超声的估计局部 PWV 的方法,但仍需要确定其临床有效性。其他技术侧重于斑块的特征描述。使用超声弹性成像,可以定量测量由于脉动压力引起的斑块应变。这项技术最初是使用血管内导管开发的,用于成像冠状动脉,但最近成功开发了非侵入性方法。已经建立了所测量的应变与破裂风险之间的高度相关性。声辐射力脉冲 (ARFI) 成像也可以根据机械特性对局部斑块成分进行特征描述。然而,弹性成像和 ARFI 都提供了组织弹性模量的间接测量。使用剪切波成像,可以定量测量弹性模量,尽管由于颈动脉的大小和几何形状,这是该技术最具挑战性的组织之一。仍需要前瞻性研究来确定这些技术对个体患者的预测价值。验证基于超声的动脉和斑块机械特征描述仍然具有挑战性。磁共振成像通常被用作斑块特征描述的“金标准”,但由于其分辨率有限,只能对斑块进行全局特征描述。CT 可提供血管树、狭窄程度和钙化斑块的信息,而软斑块特征描述仍然有限。组织学仍然是金标准,但只有在组织被切除的情况下才能获得。总之,弹性超声技术非常适合描述血管疾病的不同阶段。