Standards for quantitative assessments by coronary computed tomography angiography (CCTA): An expert consensus document of the society of cardiovascular computed tomography (SCCT)

Abstract

In current clinical practice, qualitative or semi-quantitative measures are primarily used to report coronary artery disease on cardiac CT. With advancements in cardiac CT technology and automated post-processing tools, quantitative measures of coronary disease severity have become more broadly available. Quantitative coronary CT angiography has great potential value for clinical management of patients, but also for research. This document aims to provide definitions and standards for the performance and reporting of quantitative measures of coronary artery disease by cardiac CT.

Keywords: Atherosclerosis; Computed coronary tomography angiography; Coronary plaque; Definitions.

Fig. 1.

Graphic representation of commonly reported variables by computed tomography angiography.

Fig. 2.

Semi-automated plaque segmentation by commercially available software. Extensive atherosclerosis in the left anterior descending coronary artery (LAD, panels A and B), analyzed using (semi-)automated, quantitative software by 7 different vendors: Aquarius Intuition by TeraRecon (Durham, NC; panels C and D), Qangio CT by Medis (Leiden, The Netherlands; panels E and F) Autoplaque V3.0 from Cedars-Sinai Medical Center (Los Angeles, CA; panels G and H), SyngoVia/Frontier CT Coronary Plaque Analysis by Siemens Healthineers (Forchheim, Germany; I and J). Cleerly LABS version 2.0 (Cleerly Healthcare, Denver CO; panels K and L) and HeartFlow Plaque Analysis (Mountain View, CA; panels M and N), CtaPlus by Shanghai Pulse Medial Technology, Inc. (Shanghai, China; panels O and P). The inner and outer vessel wall boundaries are segmented and the plaque in between is categorized and color-coded based on software-specific Hounsfield-unit thresholds. The location of the cross-section (left side) is indicated by an arrow on the curved (D, F, H, O) or straightened (J, L, N) longitudinal cross-section (right side). The measured minimal lumen area ranged between 1.2 mm² and 2.3 mm² and the area stenosis between 65% and 88%. The total plaque volume ranged between 76 mm³ and 486 mm³, in part reflecting differences in interrogated vessel length, as the plaque burden (total plaque/total vessel volume) had a much a narrower range between 58% and 70%, and a single outlier at 88%. The percentage non-calcified plaque volume ranged from 75% to 99%. The proportion of plaque within the lowest attenuation category varied substantially: 0.3%–35% of the total plaque volume. . (For interpretation of the references to color in this figure legend, the reader is referred to the Web version of this article.)

Fig. 3.

Classification of plaque components on CCTA based on Hounsfield Units Summary of Hounsfield-unit thresholds for classification of plaque components on CCTA from selected studies. Low-density plaque (LD), non-calcified plaque (NCP), calcified plaque (CP), necrotic core (NC), fibro-fatty plaque (FFP), fibrous plaque (FP), low-attenuation plaque (LAP), dense calcification plaque (DCP), lipid-rich plaque (LRP), fatty plaque (FaP), intermediate-attenuation plaque (IAP), low-density plaque (LDP), as defined by the original publications. Evaluation of calcific plaques.^–,–

Fig. 4.

Chronic total occlusion, coronary bifurcations, stented segment and bioresorbable examples A) Chronic total occlusion with occluded segment of 37.8mm measured along the curved reconstruction. B) Bifurcation disease (Medina classification 1, 1, 0) consisting of both predominantly calcified (proximal) and pre-dominantly non-calcified plaque (distal to the bifurcation), and measurement of the angles between the proximal left anterior descending coronary artery (LAD) and diagonal branch (Dg) and the diagonal branch and distal LAD (B). C) Metal stent in a coronary artery with no obvious in-stent disease within the treated segment (between dashed lines which are 5 mm away from the edges), although blooming and beam hardening prevent accurate evaluation of the lumen within the stent. D) Quantitative CCTA after treatment with a bioresorbable scaffold, indicated by the remaining platinum markers (arrow heads), demonstrating partially calcified plaque at the proximal edge. Area stenosis is calculated as the percentage lumen reduction at the narrowest section (minimal lumen area (MLA), arrow) relative to the averaged reference areas measured outside the treated segment (≥5 mm beyond the marker).

Fig. 5.

Interpretation of intervened coronary arteries. The treated coronary segment includes 5 mm proximal and distal to the boundaries of the stent, bioresorbable scaffold or balloon. In this example the bioresorbable scaffold has radiopaque markers at each edge (the previous site) of the scaffold.