Pulmonary artery flow artifact

Last revised by Yahya Baba on 24 Apr 2023

Pulmonary artery flow artifact, also known as pulmonary artery smoke 1, is a non-uniform contrast opacification of pulmonary arteries due to a non-homogenous contrast-blood mixing, generally due to turbulent blood flow or an early acquisition.

It is a common pitfall, often overdiagnosed as a pulmonary embolism, and usually requires a venous phase to be confirmed.

This artifact is more frequent than previously thought. Around 11% of all reported pulmonary embolisms were actually flow artifacts 2.

This artifact appears as an amorphous, ill-defined linear filling defect with a smoke-like appearance on the arterial phase, with fill-in on the venous phase 1,3.

It has a high attenuation >100 HU 1, significantly higher than expected for a true embolus (30-60 HU) 4.

There is no vessel lumen expansion (no mass effect).

It is generally bilateral in cases of early acquisition or diffuse pulmonary hypertension, and focal in cases of regional pulmonary hypertension or bronchial artery collateral inflow.

Non-opacification of the left cardiac chambers is a sign of early acquisition as contrast does not have time to opacify the distal pulmonary arteries.

There are usually background changes of pulmonary artery hypertension, bronchiectasis, and associated chronic lung disease.

In the case of focal artifact/smoke, the radiological report should include a description of the following:

  • pulmonary embolism is the most common pitfall

    • it may be hard to differentiate true emboli from smoke

    • a venous phase is often required to confirm patency of the pulmonary arteries

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