Poster Open Access

Implementing an exact algorithm for Helical CT:Removing the cone-beam artefacts

Moe, Yngve M.; Lloyd, Ryan; Tregidgo, Henry; Coban, Sophia B.; Gajjar,Parmesh; Behnsen, Julia; Turner, Martin; Lionheart, William R.B.

3-dimensional computerised tomography is usually reconstructed using the naïve Feldkamp-Davis-Kress algorithm or FDK, which is not an exact reconstruction algorithm. This caus-
es image errors, or artefacts that appear out of the central slice, and are especially visible near edges between horizontal layers - this is demonstrated in Figure 1.
To overcome these artefacts; one can perform multiple scans at different heights and combine the reconstructed volumes. However, exact reconstruction methods are necessary to
remove them altogether. These algorithms will also reduce the scanning time which makes them very attractive. Such methods exist, and Alexander Katsevich provided an algo-
rithm already in 2002[1]. His algorithm uses a helical scan-geometry, rotating the X-Ray source while moving it in parallel with the rotation axis - or, equivalently, scanning the ob-
ject while rotating it and moving it parallel to its rotation axis. In this poster, we demonstrate that it is possible to perform and reconstruct such scans, with a Nikon XTEK scanner
designed for circular scans.

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  • Adam. J. Wunderlich. The Katsevich Inversion Formula for Cone-Beam Computed Tomography. MSc. dissertation, Oregon State University, 2006.21
  • Alexander Katsevich. Theoretically exact filtered backprojection-type inversion algorithm for spiral CT. SIAM Journal on Applied Mathematics, 62(6):2012–2026, 2002.
  • Henry F.J. Tregidgo. The Implementation and analysis of Katsevich Reconstruction for helical CT. MSc. thesis, The University of Manchester, 2013.


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