Development of New Technique of Tissue Characterization of Atherosclerotic Plaque by Use of Intravascular Ultrasound

背景-纤维帽的厚度是动脉粥样硬化斑块破裂易感性的主要决定因素。已有研究表明，血管内超声(IVUS)对纤维组织的后向散射强烈依赖于超声束的入射角。这项研究探讨了使用一种新的IVUS颜色映射技术来确定动脉粥样硬化斑块中纤维帽厚度的可行性。方法和结果：使用30 MHz的IVUS导管对19个福尔马林固定的未钙化的人体动脉粥样硬化斑块进行了体外成像。静脉内超声导管相对于斑块同轴移动。选择斑块表面回声强度最大和最小的图像，计算斑块表面回声强度随角度的变化。从两个IVUS图像中获得斑块中回声强度变化的彩色表示。在彩色IVUS图像中，每个斑块表面都显示了一个边界清楚、回声强度变化很大的区域。该区域的厚度(x：mm)与组织切片纤维帽厚度(y：mm)显著相关，y=1.05x-0.01(γ=0.81p&lt；0.0001)。Bland-Altman分析也支持该方法的可靠性(平均差为0.00±0.10 mm)。结论：这项新的彩色成像技术能够准确地显示动脉粥样硬化斑块中纤维帽的厚度，是血管内超声回声强度变化的一种新方法。该方法可用于评估动脉粥样硬化斑块破裂的易感性。

Background - The thickness of the fibrous cap is a major determinant in the vulnerability of atherosclerotic plaque to rupture. It has been demonstrated that intravascular ultrasound (IVUS) backscatter from fibrous tissue is strongly dependent on the ultrasound beam angle of incidence. This study investigated the feasibility of using a new IVUS color mapping technique representing the angle-dependent echo-intensity variation to determine the thickness of the fibrous cap in atherosclerotic plaque. Methods and Results - Nineteen formalin-fixed noncalcified human atherosclerotic plaques from necropsy were imaged in vitro with a 30 MHz IVUS catheter. The IVUS catheter was moved coaxially relative to the plaque. The images showing maximum and minimum echo-intensity of the plaque surface were selected to calculate the angle-dependent echo-intensity variation. A colorized representation of the echo-intensity variation in the plaque was obtained from the two IVUS images. A clearly bordered area with large variation in echo-intensity was revealed for each plaque surface in the colorized IVUS image. The thickness (x: mm) of this area correlated significantly with that of fibrous cap (y: mm) measured from histologically prepared sections, as: y = 1.05x - 0.01 (γ=0.81, p<0.0001). Bland-Altman analysis also supported the reliability of this method (mean difference, 0.00±0.10 mm). Conclusions -This novel technique for color mapping the echo-intensity variation in IVUS provided an accurate representation of the thickness of the fibrous cap in atherosclerotic plaque. This method may be useful in assessing plaque vulnerability to rupture in atherosclerosis.