(A) Normal vessel wall is characterized by 3-layered architecture, comprising a high backscattering, thin intima (i), a low backscattering media (m), a high backscattering adventitia (a), internal elastic membrane as the border between the intima and media (blue arrow), and external elastic membrane as the border between the media and the adventitia (yellow arrow). (B) Intimal thickening occurs during the early phase of atherosclerosis in the coronary artery, which is represented as a signal-rich thick intimal band (double-headed arrow). (C) Fibrous plaque exhibits homogeneous, signal-rich (highly backscattering) regions (asterisk). (D) Calcified plaque exhibits signal-poor regions with sharply delineated borders and limited shadowing (asterisk). (E) Lipid plaque exhibits signal-poor regions (asterisk) with diffuse borders and overlying signal-rich bands (double-headed arrow). (F) Thin-cap fibroatheroma (TCFA) is defined as a lipid plaque in which the minimum thickness of the fibrous cap (arrows) is less than a predetermined threshold and lipid occupies >90° in circumference.