A Moire artifact is caused by:

A Moire artifact occurs due to interference patterns created when two repetitive structures overlap, commonly seen when an image capture system includes a grid that has a frequency similar to that of the pixel structure in digital imaging. This phenomenon is not specifically associated with traditional film or standard imaging practices, but rather arises from the specific characteristics of digital systems, which can inadvertently magnify these patterns.

In digital imaging, the pixel arrangement can interact with grid lines or other regular patterns, creating a wavy or striped appearance that detracts from the clarity of the image. This is distinct from other issues that might occur in imaging, such as a faulty grid mechanism or excessive kVp, which could result in other types of artifacts or image quality problems. Understanding that this artifact emerges from the digital imaging layout rather than issues tied to the physical components like grids or ionization properties clarifies why this answer is aligned with the cause of a Moire artifact.