For possible aortic root dilation, is a CT of the chest with or without contrast recommended?

CT Chest WITH Contrast (CTA) is Required for Aortic Root Dilation

For possible aortic root dilation, CT angiography (CTA) of the chest WITH intravenous contrast is the recommended imaging modality, as contrast enhancement is essential to visualize the aortic lumen, accurately measure aortic dimensions, and assess the vessel wall—none of which can be adequately evaluated without contrast. 1, 2

Why Contrast is Essential

• CT without contrast cannot assess the aortic lumen, which is the fundamental requirement for diagnosing and measuring aortic root dilation 3
• Contrast-enhanced CTA provides critical information about the aortic lumen, wall, and surrounding structures that is necessary for accurate diagnosis and treatment planning 1
• CTA is the reference standard for aortic aneurysm diagnosis with near 100% sensitivity and 98% specificity for detecting thoracic aortic pathology 2
• The 3D dataset from CTA allows for precise measurements perpendicular to the flow lumen, which is essential for accurate assessment of aortic root dimensions 1, 2

Optimal Imaging Protocol

• ECG-gated CTA is particularly important for the ascending aorta and aortic root to minimize cardiac motion artifacts and ensure accurate orthogonal measurements 3, 1, 2
• Multiplanar reconstructions and 3D rendering are essential components of the CTA examination for comprehensive evaluation 1, 2
• The scan should include the entire thoracic aorta from the aortic root through the descending aorta 1

When Non-Contrast CT Has Limited Value

• Non-contrast CT can only infer aortic pathology indirectly by identifying displaced aortic calcifications, but this approach has significantly lower sensitivity (71-94%) compared to CTA 3
• Non-contrast CT may identify aneurysmal dilation but cannot provide the detailed luminal assessment required for accurate measurement and characterization 4
• CT without contrast has little value in the diagnosis of aortic root pathology as it cannot adequately visualize the vessel lumen or wall 3

Alternative Imaging When Contrast is Contraindicated

• MRA (magnetic resonance angiography) is the appropriate alternative when patients have contraindications to iodinated contrast, such as severe renal insufficiency 2
• MRA provides comparable accuracy to CTA for thoracic aortic measurements, with no significant differences between the two modalities 3
• Non-contrast MRA sequences (such as balanced steady-state free precession) can provide excellent visualization of the aortic lumen without requiring gadolinium contrast 3

Common Pitfalls to Avoid

• Do not order non-contrast CT chest for suspected aortic root dilation, as it will not provide adequate assessment of the aortic lumen and will likely require repeat imaging with contrast 3, 1
• Ensure ECG gating is used for aortic root imaging to avoid motion artifacts that can lead to inaccurate measurements 3, 1, 2
• Measurements must be made perpendicular to the long axis of the aorta (not simply in the axial plane) using multiplanar reconstructions for standardized evaluation 1, 2