====== CT artifact ======

In [[computed tomography]] (CT), the term [[artifact]] is applied to any systematic discrepancy between the CT numbers in the reconstructed image and the true attenuation coefficients of the object.

===== Epidemiology =====

CT [[artifact]]s are common and can occur for various reasons. Knowledge of these artifacts is important because they can mimic [[pathology]] (e.g. partial volume artifact) or can degrade image quality to non-diagnostic levels.

Patient motion, which generates conflicts within the developed projection data, is a major cause of artifacts in clinical x-ray computed tomography (CT).

===== Classification =====


CT artifacts can be classified according to the underlying cause of the artifact. 

==== Patient-based artifacts ====

motion artifact

transient interruption of contrast

clothing artifact

jewelry artifact

==== Physics-based artifacts ====

beam hardening 

cupping artifact

streak and dark bands

[[metal artifact]] / high-density foreign material artifact

partial volume averaging

quantum mottle (noise)

photon starvation

aliasing

truncation artifact

==== Hardware-based artifacts ====

ring artifact

tube arcing

out-of-field artifact

air bubble artifact

helical and multichannel artifact

windmill artifact

cone beam effect

multiplanar reconstruction (MPR) artifact

zebra artifact

stair step artifact

====== Prevention ======

It is known that metal artifacts can be reduced by modifying standard acquisition and reconstruction, by modifying projection data and/or image data and by using virtual monochromatic imaging extracted from dual-energy CT.