Comparison between a new reconstruction algorithm (OPED) and filtered backprojection (FBP) for MDCT data
2012
Previously the Orthogonal Polynomial Expansion on the Disk (OPED) algorithm was presented. Further, in
prototype experiments in combination with the CT D`or geometry feasibility was demonstrated. In this study
we implemented OPED with a clinical Scanner, and evaluated the potential using phantom studies.
All studies were acquired on a Siemens Somatom 64 (Erlangen, Germany) scanner, where raw projection data
were reconstructed with the conventional FBP reconstruction and the OPED algorithm. OPED allows one to
use fan beam geometry directly without any additional procedures such as interpolation or rebinning if using
the CT D`or geometry. In particular, OPED describes an approximation of the image function as a sum of
polynomials using Chebychev polynomials. For performance evaluation, the Catphan phantom 600 was
imaged. OPED Images where reconstructed using C++ and MATLAB® .We measured uniformity, MTF and
CNR for different dose levels and compared these to standard FBP images reconstructions with different filter
kernels.
The integration and interpretation of the MDCT projection data for the OPED algorithm was accomplished.
Reconstruction time is about 6 s on Quad-Core 3 GHz Intel Xeon processor. Typical artifacts are reduced
when applying OPED. Using OPED the MTF maintains constant over the whole FOV. Uniformity and CNR
are equal compared to FBP.
Advantages of OPED were demonstrated by applying the algorithm to projections images from a clinical
MDCT scanner. In the future, we see OPED applications for low-dose or limited angle geometries to reduce
the radiation dose while improving diagnostic quality of the reconstructed slices.
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