Stair-step artifacts in three-dimensional helical CT: an experimental study.
OBJECTIVE
Stair-step artifacts in helical computed tomography (CT) are associated with inclined surfaces in longitudinal sections. The authors investigated the origin and the characteristics of the artifacts.


METHODS
A cone phantom and a skull were dry-scanned with a helical CT scanner, and images were reconstructed by using the half-scan interpolation algorithm with combinations of detector collimation (1 and 5 mm), table feed (1, 2, 5, and 10 mm), and reconstruction interval (1, 2, 5, and 10 mm).


RESULTS
Stair-step artifacts were perceived in most instances. Stair-step artifacts arose from two sources: large reconstruction intervals and asymmetric helix interpolation, forming isoclosed curves and spirallike patterns in three-dimensional axial views, respectively.


CONCLUSIONS
To eliminate the stair-step artifacts, both the collimation and the table feed should be less than the longitudinal dimension of the important feature on inclined surfaces, and the reconstruction interval should be less than the table feed. Adaptive interpolation may correct the artifacts.
Wang
G
G
Division of Radiology Research, Mallinckrodt Institute of Radiology, Washington University School of Medicine, St Louis, MO 63110.
Vannier
M W
MW
D016477:Artifacts; D006801:Humans; D007091:Image Processing, Computer-Assisted; D066298:In Vitro Techniques; D008961:Models, Structural; D012886:Skull / Q000000981:diagnostic imaging; D014057:Tomography, X-Ray Computed