Hiro T, Leung C Y, Karimi H, Farvid A R, Tobis J M
Division of Cardiology, University of California, Irvine, Orange 92668-3298, USA.
Am Heart J. 1999 Mar;137(3):476-81. doi: 10.1016/s0002-8703(99)70495-3.
Intravascular ultrasound (IVUS) images vary in intensity because of the angle of the transducer relative to the plaque. The purpose of this study was to determine the angle dependence of ultrasound backscatter when the IVUS transducer is aligned coaxially in atherosclerotic arteries and to examine its feasibility in tissue characterization of human atherosclerotic tissue.
Thirty-nine noncalcified regions of interest (ROI, 0.4 to 0. 6 mm in diameter) within cross sections of formalin-fixed human iliac arterial plaque were imaged with a 3.9F, 25-MHz IVUS catheter in saline at room temperature. The catheter was moved coaxially from 8 to 16 positions and spanned 50 to 122 degrees relative to the ROI and the lumen center. Echo intensity for each ROI was defined as the videointensity relative to a standard reflector. The angle dependence of echo intensity was defined as the slope of the regression line between the angle of incidence and echo intensity. Each ROI was histologically classified into 4 groups: fibro-acellular (fibrous cap, n=7), fibro-cellular (n=9), fibro-fatty (n=13), or fatty tissue (n=10). The echo intensity of the majority (72%) of plaque components in IVUS images are significantly affected by the angle of incidence of the transducer. The angle dependence of fibro-acellular samples was significantly greater than that of the other 3 groups (4.69 +/- 3.29 x 10(-3) x echo intensity/degree vs 1.06 +/- 1.10 in fibro-cellular area, 2.09 +/- 1.75 in fibro-fatty area, and 2.16 +/- 1.92 in fatty area, P <. 05).
The angle dependence of ultrasound reflections from the fibrous cap of atherosclerotic plaque is another method of tissue characterization in addition to spatial distribution and echo intensity. This technique may be useful in determining the thickness of the fibrous cap, which may be an important predictor of plaque rupture.
由于换能器相对于斑块的角度不同，血管内超声（IVUS）图像的强度会有所变化。本研究的目的是确定当IVUS换能器在动脉粥样硬化动脉中同轴对齐时超声背向散射的角度依赖性，并检验其在人体动脉粥样硬化组织特征分析中的可行性。
在室温下，使用3.9F、25MHz的IVUS导管对福尔马林固定的人髂动脉斑块横截面内的39个非钙化感兴趣区域（ROI，直径0.4至0.6mm）在盐水中进行成像。导管相对于ROI和管腔中心同轴移动8至16个位置，跨越50至122度。每个ROI的回波强度定义为相对于标准反射体的视频强度。回波强度的角度依赖性定义为入射角与回波强度之间回归线的斜率。每个ROI在组织学上分为4组：纤维无细胞（纤维帽，n = 7）、纤维细胞（n = 9）、纤维脂肪（n = 13）或脂肪组织（n = 10）。IVUS图像中大多数（72%）斑块成分的回波强度受换能器入射角的显著影响。纤维无细胞样本的角度依赖性显著大于其他3组（4.69±3.29×10⁻³×回波强度/度，纤维细胞区域为1.06±1.10，纤维脂肪区域为2.09±1.75，脂肪区域为2.16±1.92，P <.05）。
除了空间分布和回波强度外，动脉粥样硬化斑块纤维帽的超声反射角度依赖性是另一种组织特征分析方法。该技术可能有助于确定纤维帽的厚度，而纤维帽厚度可能是斑块破裂的重要预测指标。
