Coronary CT Angiography Can Detect Both Calcified and Non-Calcified Plaque
No, coronary CT angiography (CCTA) does not only show calcified plaque but can detect both calcified and non-calcified coronary artery plaque. CCTA is capable of visualizing the full spectrum of coronary atherosclerotic plaque composition, including calcified, non-calcified (soft), and mixed plaque types.
Plaque Characterization Capabilities of CCTA
Types of Plaque Detected by CCTA
- Calcified plaque: Appears as high-density areas with high CT attenuation values
- Non-calcified plaque: Has lower CT density values, correlating with lipid-laden or fibrous tissue
- Mixed plaque: Contains both calcified and non-calcified components
According to the American Heart Association guidelines, CCTA can differentiate between plaque components based on their CT attenuation values 1:
- Non-calcified plaque: Lower CT density values
- Fibrous plaque: Intermediate density values
- Calcified plaque: High density values
Diagnostic Performance
- CCTA shows excellent sensitivity (92%) and specificity (98%) for detecting any plaque identified by optical coherence tomography 2
- For specifically identifying plaque as calcified versus non-calcified, CCTA demonstrates sensitivity of 87% and specificity of 96% 3
Technical Considerations for Plaque Assessment
Requirements for Optimal Plaque Visualization
- IV contrast administration is necessary to visualize non-calcified plaque
- ECG-gating is essential for motion-free coronary imaging
- High image quality is critical for accurate non-calcified plaque assessment 4
Limitations in Plaque Assessment
- Spatial resolution limitations affect characterization of smaller plaques
- Overlap between density values of different plaque types can make precise tissue characterization challenging
- Very small plaques (sub-millimeter) may be missed, particularly early atherosclerotic lesions 2
- Blooming artifacts from adjacent calcifications can impact assessment accuracy 4
Standardized Reporting of Plaque
The CAD-RADS 2.0 system provides a standardized framework for reporting both stenosis and plaque characteristics 1:
- Stenosis grading: 0-100% stenosis
- Plaque burden assessment: P1 (mild) to P4 (extensive)
- Plaque composition: Documentation of calcified vs. non-calcified components
For example, CAD-RADS 0 represents "absence of calcified and non-calcified plaque in the coronary tree" 1, explicitly acknowledging CCTA's ability to assess both plaque types.
Clinical Implications
The ability of CCTA to detect non-calcified plaque is particularly important because:
- Non-calcified plaque may represent earlier stages of atherosclerosis
- Certain non-calcified plaque features (low attenuation, positive remodeling) are associated with higher risk of future cardiac events
- Patients can have significant non-calcified plaque burden even with zero calcium scores 5
Comparison with Other Imaging Modalities
- Calcium scoring CT: Detects only calcified plaque; cannot reliably visualize non-calcified components
- Invasive coronary angiography: Gold standard for stenosis assessment but limited in plaque characterization
- Intravascular ultrasound/OCT: Provides superior plaque characterization but is invasive
Conclusion
CCTA is a comprehensive non-invasive imaging modality that can visualize both calcified and non-calcified coronary plaque. While calcium scoring CT is limited to detecting calcified plaque only, CCTA with contrast enhancement allows for assessment of the full spectrum of atherosclerotic plaque composition, making it a valuable tool for comprehensive coronary artery disease evaluation.