Windmill artifact

In CT imaging, the windmill artifact is an image distortion in the axial plane, encountered during helical multidetector acquisitions. The telltale appearance is characterized by equally distanced bright streaks diverging from a focal high-density structure. The streaks seemingly rotate while scrolling back and forth through the affected slices - hence the name .

The windmill artifact is caused by inadequate data sampling in the z-plane, due to multiple detector rows intersecting the reconstruction plane during each rotation of the gantry. With increasing the helical pitch the number of detector rows intersecting the same image plane also increases, thus resulting in an increased amount of streaks . The windmill artifact can be therefore ameliorated by either decreasing the pitch or using axial acquisition technique instead .