Baldewsing Radj A, Schaar Johannes A, de Korte Chris L, Mastik Frits, Serruys Patrick W, van der Steen Antonius F W
Thoraxcenter, Erasmus MC, Rotterdam, The Netherlands.
Stud Health Technol Inform. 2005;113:75-96.
The material composition and morphology of the atherosclerotic plaque components are considered to be more important determinants of acute coronary ischemic syndromes than the degree of stenosis. When a vulnerable plaque ruptures it causes an acute thrombotic reaction. Rupture prone plaques contain a large lipid pool covered by a thin fibrous cap. The stress in these caps increases with decreasing thickness. Additionally, the cap may be weakened by macrophage infiltration. IntraVascular UltraSound (IVUS) elastography might be an ideal technique to assess the presence of lipid pools and to identify high stress regions. Elastography is a technique that assesses the local elasticity (strain and modulus) of tissue. It is based on the principle that the deformation of tissue by a mechanical excitation is a function of its material properties. The deformation of the tissue is determined using ultrasound. For intravascular purposes, the intraluminal pressure is used as the excitation force. The radial strain in the tissue is obtained by cross-correlation techniques on the radio frequency signals. The strain is color-coded and plotted as a complimentary image to the IVUS echogram. IVUS elastography, and IVUS palpography (which uses the same principle but is faster and more robust), have been extensively validated using simulations and by performing experiments in vitro and in vivo with diseased arteries from animals and humans. Strain was shown to be significantly different in various plaque types (absent, fatty, fibrous or calcified). A high strain region with adjacent low strain at the lumen vessel-wall boundary has 88% sensitivity and 89% specificity for detecting vulnerable plaques. High strain regions at the lumen plaque-surface have 92% sensitivity and 92% specificity for identifying macrophages. Furthermore, the incidence of vulnerable-plaque-specific strain patterns in humans has been related to clinical presentation (stable angina, unstable angina or acute myocardial infarction) and the level of C-reactive protein. In conclusion, the results obtained with IVUS (strain and modulus) elastography/palpography, show the potential of the technique to become a unique tool for clinicians to assess the vulnerability and material composition of plaques.
与狭窄程度相比，动脉粥样硬化斑块成分的物质组成和形态被认为是急性冠状动脉缺血综合征更重要的决定因素。当易损斑块破裂时，会引发急性血栓反应。易破裂斑块含有一个由薄纤维帽覆盖的大脂质池。这些纤维帽中的应力会随着厚度的减小而增加。此外，巨噬细胞浸润可能会削弱纤维帽。血管内超声（IVUS）弹性成像可能是评估脂质池的存在并识别高应力区域的理想技术。弹性成像是一种评估组织局部弹性（应变和模量）的技术。它基于这样一个原理，即机械激发引起的组织变形是其材料特性的函数。组织的变形通过超声来确定。对于血管内应用，腔内压力用作激发力。通过对射频信号进行互相关技术获得组织中的径向应变。应变以颜色编码并作为IVUS回波图的补充图像绘制出来。IVUS弹性成像和IVUS触诊成像（使用相同原理，但速度更快且更可靠）已通过模拟以及在体外和体内对动物和人类的病变动脉进行实验得到广泛验证。结果表明，不同斑块类型（无、脂肪、纤维或钙化）的应变存在显著差异。在管腔血管壁边界处具有相邻低应变的高应变区域检测易损斑块的灵敏度为88%，特异性为89%。管腔斑块表面的高应变区域识别巨噬细胞的灵敏度为92%，特异性为92%。此外，人类中易损斑块特异性应变模式的发生率与临床表现（稳定型心绞痛、不稳定型心绞痛或急性心肌梗死）以及C反应蛋白水平有关。总之，IVUS（应变和模量）弹性成像/触诊成像所获得的结果表明，该技术有可能成为临床医生评估斑块易损性和物质组成的独特工具。
