Objective:

To review established and emerging noninvasive ultrasound techniques for assessing atherosclerotic plaques, including methods for identifying plaque vulnerability and monitoring progression.

Approach:

• Introduction: Reviews the role of atherosclerosis in cardiovascular disease and the potential value of assessing plaque vulnerability beyond the degree of stenosis.
• Plaque Phenotype and Risk Assessment: Examines associations between carotid plaques and cardiovascular event risk, emphasizing the importance of identifying unstable or rapidly progressive plaques.
• Morphological Analysis: Describes current carotid plaque definitions and classifications and evaluates morphological features associated with plaque vulnerability and adverse outcomes.

Key Findings:

• The presence of carotid plaques is associated with significant 10-year cardiovascular event risk, with higher risk reported for bilateral carotid plaques or a carotid plaque accompanied by a plaque at the femoral bifurcation.
• Plaque ulceration, surface irregularity, intraplaque hemorrhage, lipid-rich necrotic core, and neovascularization are associated with plaque vulnerability.
• Three-dimensional ultrasound detects carotid plaque ulcerations more effectively than two-dimensional ultrasound, but technical complexity, cost, and difficulty assessing heavily calcified plaques limit routine use.

Interpretation:

Evaluating plaque morphology and composition may complement stenosis measurement and clinical variables to improve cardiovascular risk stratification.

Limitations:

• Plaque definitions, classifications, measurement methods, and clinically relevant thresholds remain insufficiently standardized.
• Specialized three-dimensional ultrasound equipment and analysis are costly, complex, and time-consuming.
• Heavily calcified plaques remain difficult to assess with two-dimensional or three-dimensional ultrasound.

Conclusion:

Advances in ultrasound—including three-dimensional imaging, contrast-enhanced ultrasound, microvascular flow imaging, ultrafast ultrasound imaging, and elastography—enable more detailed plaque assessment. Standardized protocols are needed, and multiparametric scores require prospective validation and correlation with clinical outcomes before routine clinical use.