Chapter 25. Adjunctive Diagnostic Techniques: Intravascular Ultrasound, Optical Coherence Tomography, and Spectroscopy
Which of the following statements is correct in terms of intravascular ultrasound (IVUS) findings of the coronary artery?
A. Arterial 3-layer structures (intima, media, and adventitia) generally correspond to a high–low–high echoic appearance of the arterial wall on IVUS images.
B. The thickness of intima decreases with age.
C. The media is clearly observed as a distinct layer, especially in atherosclerotic lesions.
D. Plaque vulnerability can be accurately evaluated by conventional gray-scale IVUS.
Interpretation of intravascular ultrasound (IVUS) images relies on the fact that arterial wall structures can be identified as separate layers. Typically, the differences in acoustic impedance of intima, media, and adventitia of coronary arteries give rise to a characteristic 3-layered (high–low–high) appearance on IVUS images (choice A). In muscular arteries such as the coronary tree, the media generally stands out as a thin dark layer since it contains much less echo-reflective material (collagen and elastin) than the neighboring intima and adventitia. However, this layered appearance may be undetectable in truly normal coronary arteries wherein the intimal thickness is below the effective resolution of IVUS. Also, with progression of atherosclerosis and/or patient age, the intima/plaque layer increases in thickness (choice B), and the media may be destroyed so that it may not appear as a distinct layer around the full circumference of the vessel (choice C). With respect to plaque vulnerability assessment, visual interpretation of conventional gray-scale IVUS images is limited in the precise detection and quantification of specific plaque components (choice D). Low echogenicity of plaque may represent its lipid content, but a similar appearance can result from other conditions, such as acoustic shadowing from microcalcifications or an adjacent region of calcification or fibrosis.
An intravascular ultrasound (IVUS) image was obtained within a stented segment from a patient who underwent stent implantation 12 months ago. What is the area indicated in yellow?
B. Neointimal hyperplasia (or thrombus) area
D. Plaque plus media area
On intravascular ultrasound (IVUS) scan, metallic stent struts are visualized as bright, focal points in a circular-arrayed pattern, and the stent area measurement is performed at the leading edge of these distinct echoes (a blue line on the right panel). Neointimal hyperplasia within the stent has low echo-reflectivity at follow-up IVUS imaging, and the area is calculated as the difference between stent ...