How are artifacts defined in imaging?

Artifacts in imaging are defined as anything appearing on the image that is not present in the object scanned. This means that artifacts do not contribute to the actual representation of the scanned object and can be caused by a variety of factors including technical errors, beam hardening, or motion during the scan. Recognizing and understanding artifacts is crucial for image interpretation, as they can misleadingly alter the appearance of relevant structures, which could lead to misdiagnosis.

The other options do not accurately capture the essence of what artifacts are. Visual representations of historical data, necessary adjustments to improve image quality, and completed images that require no further processing relate to different aspects of imaging and do not align with the definition of artifacts.