Artifacts associated with implementation of the Grangeat formula

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To compensate for image artifacts introduced in approximate cone-beam reconstruction, exact cone-beam reconstruction algorithms are being developed for medical x-ray CT. Although the exact cone-beam approach is theoretically error-free, it is subject to image artifacts due to the discrete nature of numerical implementation. We report a study on image artifacts associated with the Grangeat algorithm as applied to a circular scanning locus. Three types of artifacts are found, which are thorn, wrinkle, and V-shaped artifacts. The thorn pattern is created by inappropriate extrapolation into the shadow zone in the radon domain. If the shadow zone is filled in with continuous data, the thorn artifacts along the boundary of the shadow zone can be removed. The wrinkle appearance arises if interpolated first derivatives of the radon data are not smooth between adjacent detector planes. In particular, the nearest-neighbor interpolation method should not be used. If the number of projections is not small, the bilinear interpolation method is effective to suppress the wrinkle artifacts. The V-shaped artifacts on the meridian plane come from the line integrations through the transition zones where derivative data change abruptly. Two remedies are to increase the sampling rate and suppress data noise. (C) 2002 American Association of Physicists in Medicine.
Publisher
AMER ASSOC PHYSICISTS MEDICINE AMER INST PHYSICS
Issue Date
2002-12
Language
English
Article Type
Article
Keywords

CT

Citation

MEDICAL PHYSICS, v.29, no.12, pp.2871 - 2880

ISSN
0094-2405
URI
http://hdl.handle.net/10203/81800
Appears in Collection
NE-Journal Papers(저널논문)
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