CTICasesAortic Contrast Mixing Artifact
Imaging findings
Chest CT angiography in a 91-year-old lady scanned after a fall shows a hyperdense pseudoflap along the lesser curve and undersurface of the aortic arch on early arterial phase images, simulating a minimal aortic injury or dissection flap. There is a lack of mediastinal hematoma or retrosternal fluid, and the artifact disappears on routine windows, showing high attenuation values (>200 HU) consistent with aortic contrast smoke.
Key takeaways
Contrast mixing artifact (or contrast smoke) along the lesser curvature of the aortic arch is a well-recognized diagnostic pitfall on chest CT, particularly in older patients with low cardiac output or turbulent flow. High-density contrast layers and mixes poorly with unopacified blood in areas of slow flow, mimicking a dissection or traumatic aortic injury. Evaluating attenuation values and verifying the absence of secondary signs of trauma helps avoid misdiagnosis.
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