Artifacts associated with implementation of the Grangeat formula

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...

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Bibliographic Details
Published in:Medical physics (Lancaster) Vol. 29; no. 12; pp. 2871 - 2880
Main Authors: Lee, Seung Wook, Cho, Gyuseong, Wang, Ge
Format: Journal Article
Language:English
Published: United States American Association of Physicists in Medicine 01.12.2002
Subjects:
algorithm theory
Algorithms
Biophysics - methods
Computed radiography
Computed tomography
computed tomography (CT)
computerised tomography
Cone beam computed tomography
cone‐beam CT
exact reconstruction
Image analysis
Image Processing, Computer-Assisted - methods
image reconstruction
Image reconstruction; tomography
Interpolation
Medical image artifacts
Medical image noise
medical image processing
Medical image reconstruction
Medical imaging
Medical X‐ray imaging
Models, Theoretical
Number theory
Radon
Tomography, X-Ray Computed - methods
X‐ray imaging
artifact
computed tomography (CT)
cone-beam CT
exact reconstruction
ISSN:0094-2405, 2473-4209
Online Access:Get full text
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Summary: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.
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ISSN:0094-2405
2473-4209
DOI:10.1118/1.1522748