Review Article
Methods of plaque quantification and characterization by cardiac computed tomography

https://doi.org/10.1016/j.jcct.2009.10.012Get rights and content

Abstract

The pathologic evolution of coronary artery atherosclerosis occurs slowly over decades, which may provide an opportunity for diagnostic imaging to identify patients before clinical events evolve. Cardiac computed tomography (CT) is an emerging noninvasive imaging tool, which can visualize the entire coronary tree with submillimeter resolution. We reviewed the current status of cardiac CT to qualitatively and quantitatively determine coronary plaque dimensions and composition, and its potential to improve our understanding of the natural history of coronary artery disease as well as prevention of cardiovascular events.

Section snippets

Background

Even though effective treatment strategies to lower coronary event risk are available, an estimated 1.3 million Americans will have a myocardial infarction in 2009, and approximately 37% of these Americans will die of it.1 A main reason for these devastating statistics is that between 50% and 60% of myocardial infarctions occur in previously asymptomatic persons with no significant coronary artery stenosis. In the majority of the cases (two-thirds), the rupture of a thin cap fibroatheroma and

Current methods of plaque quantification and characterization

IVUS is a catheter-based imaging technique, which permits the assessment of atherosclerotic plaque in clinical practice and research. It is considered as the clinical “gold standard” for detection and quantification of coronary plaques.8 IVUS with a spatial resolution of approximately 150 microns permits visualization of normal vessel wall and early atherosclerotic lesions.9 Cross-sectional analysis of IVUS images permits the measurements of atheroma dimensions with a close correlation to

Coronary CT imaging

Multidetector-row CT (MDCT) permits imaging of calcified coronary atherosclerotic plaque using noncontrast scan and the additional detection of noncalcified plaque and luminal narrowing by using contrast-enhanced image acquisition.

Detection of coronary plaque by MDCT

The newest MDCT technology with gantry rotation times of 270–350 milliseconds, temporal resolution of 75–106 milliseconds, coverage in z-direction of 3.2–16 cm, and isotropic resolution of 0.4 mm now provides technical prerequisites for coronary atherosclerotic plaque imaging.16, 17, 18, 19, 20, 21, 22 Thus, research targeting the qualitative and quantitative assessment of coronary plaque, including assessment of plaque size, composition, and remodeling is feasible.20, 23, 24, 25

The normal

Quantification of coronary plaque

Because of the 3-dimensional nature of CT data sets and the ability to reconstruct multiplanar-reformatted images cross-sectional and perpendicular to the vessel centerline, MDCT may be able to characterize individual plaque morphology and composition as well as total plaque burden similar to IVUS.9 The most widely used MDCT metrics for plaque size are based on area and volume measurements. The cross-sectional view of the vessel permits the assessment of the lumen area and outer vessel area.20

Assessment of coronary plaque composition

There is great morphologic heterogeneity of coronary atherosclerotic plaques (Fig. 1). Few studies investigating the ability of MDCT to quantitatively assess plaque composition have been conducted (4- [n = 4], 16- [n = 4], and 64-slice MDCT [n = 3]). Typically, investigators performed Hounsfield unit (HU) measurements to determine the ability of CT to differentiate between calcified and noncalcified and furthermore between lipid-rich and fibrous plaque compared with IVUS scanning or histology.

Potential clinical applications: Culprit lesions in ACS

Quantitative assessment of plaque composition and remodeling has been studied in the context of culprit lesions in acute coronary syndrome (ACS). The concept of MDCT plaque characterization in patients with ACS was introduced in a recent study, which showed that culprit lesions have a greater plaque area and higher RI than stable lesions (17.5 ± 5.9 mm2 versus 9.1 ± 4.8 mm2 and 1.4 ± 0.3 versus 1.0 ± 0.3 mm, respectively).55 A subsequent study showed that the presence of noncalcified plaque

Conclusion

Cardiac CT, with its ability to noninvasively detect and characterize coronary atherosclerotic plaque, is uniquely suited to deepen our understanding of the natural history of CAD and to potentially predict cardiovascular events on an epidemiologic and individual level. Major research efforts are required to standardize imaging and plaque assessments and to validate criteria for the differentiation of low- and high-risk plaque. Refinement of semiautomated plaque quantification, in combination

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    Conflict of interest: The authors report no conflicts of interest.

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    Copyright © 2009 Society of Cardiovascular Computed Tomography. Published by Elsevier Inc. All rights reserved.