MOTION ARTIFACTS IN THE X-RAY CT IMAGE OF A REVOLVING POINT OBJECT

To obtain the cross section of an object by using an X-ray CT scanner, many projections of the object with various angles are required. This also takes time for scanning. If the object moves during this period, the projections would be disturbed causing motion artifact in the CT image. Understanding of their characteristics in relation to the movements of the objects will be useful for analyzing CT images and will supply new knowledge to medical diagnosis. This paper investigates a reconstructed image of a point object which revolves around the center of a scanning area. The results show that the reconstructed image of the point object forms an epicycloid or hypocycloid (a curve on a plane) and this reduces with time. The same type of artifact is simulated by a computer, and this justifies the analysis.