A resident's one-poster guide to common CT artifacts:

S. R. Chaudhary , L. C. Smith , V. Chidambaram

Royal Liverpool and Broadgreen University Hospitals United Kingdom 

"Mixing artifact - This occurs when blood containing contrast (bright) in arteries mixes with blood in the veins (darker), giving an appearance of a thrombus. This is usually confirmed by doing a more delayed phase study (Fig. 12 on page 13)." 

"Einen diagnostischen „pitfall“ stellt die physiologische Durchmischung von kontrastiertem mit nichtkontrastiertem Blut dar, die insbesondere in den Nierenvenen zu erheblichen Flussartefakten führen kann, welche nicht mit Thrombosen verwechselt werden dürfen."

https://slidex.tips/download/bildgebung-bei-k...

Is this CT angio? In which case, I think it refers to eine Durchmischung des Kontrastmittels that may be mistaken for a filling defect/thrombus.

“Pitfalls and artefacts in CT pulmonary angiography

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Fig: Axial CT image in a poorly opacified study. Poor mixing of contrast has resulted in inhomogenous opacification of the left pulmonary artery and a pseudo-filling defect in the proximal lingular artery which is unconvincing on mediastinal windows.

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The key feature that distinguishes these mixing artefacts is the distal end of the column of unopacified blood.”

https://posterng.netkey.at/esr/viewing/index....