Fig. 4: Imaging modalities for the assessment of coronary stenosis.

a, CT obtained from a man aged 62 years with atypical chest pain and severe aortic stenosis. Straight reformation (left panel) of the right coronary artery (RCA) demonstrates several calcified plaques and a 40% diameter stenosis of the mid-RCA (arrow), which is confirmed by invasive coronary angiography (ICA; arrow in the middle panel). The severity of the stenosis (right panel) is based on the ratio of the minimal lumen diameter (MLD; blue line) and the average luminal diameter of the reference regions. b, MRI demonstrates a curved reformation (left panel) of the left anterior descending coronary artery. Both imaging modalities (MRI and CT) identified a >50% luminal diameter stenosis in the proximal left anterior descending coronary artery (arrows). The right panel demonstrates luminal dimension differences between MRI and CT. c, An intravascular ultrasonography (IVUS)-derived cross-sectional image of the RCA from an individual without coronary artery disease (left panel), with the IVUS catheter located centrally in the lumen. Note that, in normal coronary vessels, the wall is shown as a thin echogenic layer (arrow) delineated by two low-echogenic layers that correspond to the intima and adventitia. In comparison, an obstructive coronary plaque in the RCA (middle panel) with a thickened wall causes a 50% diameter stenosis. Stenosis severity assessed by IVUS (right panel) can also be estimated as minimal lumen area (MLA; green line) or MLD (blue line); note that the high penetration depth of IVUS allows the visualization of the outer layers of the vessel wall. d, Cross-sectional optical coherence tomography (OCT) image from the mid-segment of the left circumflex coronary artery for assessment of an obstructive lesion with an 81% area stenosis and a 56% diameter stenosis (left panel). Quantitative ICA (middle panel) yields an area stenosis of 96% and a diameter stenosis of 79%, illustrating that lumen dimensions measured by OCT are larger and yield a less severe stenosis grade compared with the use of ICA⁷⁹. The graphical representation of the OCT axial image (right panel) compares the estimation of stenotic lesion based on MLA and MLD determined in the stenotic segment. D, distal; P, proximal.