It is a dense line on the image at a specific point. ZIPPER ARTIFACT
Most of them are related to hardware or software problems beyond the technologist immediate control. This can also be caused by the extraneous RF entering the room at a certain frequency, and interfering with the inherently weak signal coming from the patient RF from some radio transmitters will cause zipper artifacts that are oriented perpendicular to the frequency axis of your image. CAUSE
Frequently there is more than one artifact line on an image from this cause. Other equipment and software problems can cause zippers in either axis. It is cause by a leak in the RF shielding of the Room CAUSE
Ensure that the door is properly closed during image acquisition. Call the engineer and repair the leak in RF shielding REDUCTION