Imaging Modalities for Detecting Non-Calcified Atherosclerotic Plaques (NCPs)
Imaging Modalities for Detecting Non-Calcified Atherosclerotic Plaques (NCPs):
Non-calcified plaques (NCPs) represent lipid-rich, fibrous, or inflamed lesions that may not be detected by traditional calcium scoring. Multiple imaging modalities beyond CT can help identify such plaques—either anatomically or by detecting biological activity.
1. Cardiac MRI (CMR)
• Type: Non-invasive, no ionizing radiation
• Capabilities:
• Wall thickness and vessel remodeling
• T1/T2 mapping may help characterize fibrous vs lipid-rich plaques
• Contrast-enhanced MR angiography can partially show vessel lumen
• Limitations:
• Limited spatial resolution for coronary arteries
• Used primarily for large vessels (e.g., carotid, aorta)
• Role: Research and selective clinical use for vascular inflammation or plaque burden
2. Intravascular Ultrasound (IVUS)
• Type: Invasive (catheter-based)
• Capabilities:
• Direct imaging of vessel wall and plaque burden
• Differentiates calcified from non-calcified plaque
• Role: Gold standard for plaque volume and burden in PCI settings
3. Optical Coherence Tomography (OCT)
• Type: Invasive (high-resolution catheter)
• Capabilities:
• Ultra-high resolution (~10 µm)
• Visualizes fibrous cap thickness, lipid cores, and plaque rupture
• Limitations:
• Requires blood clearance with contrast
• Small imaging depth
• Role: Best for characterizing vulnerable plaques in acute coronary syndrome
4. Carotid Ultrasound
• Type: Non-invasive
• Capabilities:
• Identifies plaque morphology and intima-media thickness (IMT)
• May detect soft plaques in carotids but not coronary arteries
• Role: Screening tool for systemic atherosclerosis in asymptomatic individuals
5. PET Imaging (Positron Emission Tomography)
• Type: Functional/biological imaging
• Radiotracers:
• FDG (18F-fluorodeoxyglucose) → detects macrophage-driven inflammation
• NaF (18F-sodium fluoride) → detects microcalcification, an early feature of plaque destabilization
• Applications:
• Identifying biologically active (vulnerable) plaques
• Evaluating response to therapies (e.g., statins)
• Limitations:
• Low spatial resolution
• Coronary imaging is challenging due to cardiac motion and myocardial FDG uptake
• Role: Primarily research, selective use in large-vessel atherosclerosis
6. PET/MRI (Hybrid Imaging)
• Type: Combined molecular and anatomical imaging
• Capabilities:
• PET: Detects inflammation or microcalcification
• MRI: Assesses plaque morphology, intraplaque hemorrhage, vessel remodeling
• Synergistic view of plaque biology + structure
• Advantages:
• Reduced radiation compared to PET/CT
• Superior soft tissue contrast from MRI
• Limitations:
• High cost, limited availability
• Still under research for coronary arteries
• Role: Ideal in research and high-risk carotid/aortic imaging; expanding clinical interest
