Fig. 9: IVUS for quantitative coronary atherosclerosis imaging.

Intravascular ultrasonography (IVUS) plaque detection and quantification. a, Positive remodelling is the thickening of the vessel wall secondary to coronary plaques (Fig. 2); in this example, the thickened wall (arrows) has already narrowed the vessel lumen (top panel). Plaque burden is calculated as the ratio of the atheroma area to the external elastic lamina of the vessel (arrows); the atheroma area is calculated by the difference between the external elastic lamina area and the lumen area (middle panel). Calcified plaque (arrows) causes acoustic shadowing, obscuring the external layers of the vessel wall (bottom panel). b, IVUS artefacts. Differentiating artefacts from true structures in IVUS is pivotal for plaque assessment. Acoustic shadowing behind calcific plaque (asterisks; top panel). Reverberation artefact can be seen as multiple equidistant reflections from calcium (arrows; middle panel). Non-uniform rotational distortion is seen along the curved dotted line (bottom panel). c, Optimal stent implantation by IVUS guidance. For optimal stent implantation (Fig. 2), the following criteria must be met: a plaque burden of <50% at 5 mm proximal or distal to the plaque edge (top panel), stent expansion at the minimal lumen area must be >5.0 mm² or 90% of the minimal lumen area of the reference segments (middle panel), and no dissection of >3 mm involving the media¹⁴¹ (bottom panel). d, Criteria for stent failure are plaque overload of >50% (top panel), underexpansion (middle panel) and edge dissection (bottom panel).