CTICasesPseudo-Pulmonary Embolism (Mixing Phenomenon / Smoke Artifact)
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Imaging findings
Extremely bright opacification (750-800+ HU) of the pulmonary arteries due to very early scanning and a leading bolus of contrast. Apparent intraluminal filling defects are noted, particularly conspicuous in the pulmonary arteries. Quantitative analysis of these "defects" reveals high Hounsfield units (e.g., 434-462 HU), indicating relatively less opacified blood mixing with highly opacified blood, rather than true low-attenuation thrombus.
Key takeaways
This case is a classic example of pseudo-pulmonary embolism, a common artifact caused by a mixing phenomenon of highly concentrated contrast with relatively unopacified blood in the pulmonary arteries, often seen with early-phase scanning. It's crucial to differentiate these "smoke artifacts" from true pulmonary emboli by assessing Hounsfield units within the apparent filling defects, as misinterpretation can lead to unnecessary treatment. The simultaneous brightness contrast illusion can also contribute to this visual perception.
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