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Med Phys. 2016 May;43(5):2344. doi: 10.1118/1.4945418.

Filtered-backprojection reconstruction for a cone-beam computed tomography scanner with independent source and detector rotations.

Author information

1
Université de Lyon, CREATIS, CNRS UMR5220, Inserm U1044, INSA-Lyon, Université Lyon 1, Department of Radiation Oncology, Centre Léon Bérard, 28 rue Laennec, Lyon 69008, France.
2
Laboratoire Hubert Curien, CNRS and Université Jean Monnet (UMR5516), 18 rue du Professeur Benoit Lauras, Saint Etienne F-42000, France.
3
Institute for Research and Development on Advanced Radiation Technologies (radART), Paracelsus Medical University, Strubergasse 16, Salzburg 5020, Austria and medPhoton GmbH, Strubergasse 16, Salzburg 5020, Austria.

Abstract

PURPOSE:

A new cone-beam CT scanner for image-guided radiotherapy (IGRT) can independently rotate the source and the detector along circular trajectories. Existing reconstruction algorithms are not suitable for this scanning geometry. The authors propose and evaluate a three-dimensional (3D) filtered-backprojection reconstruction for this situation.

METHODS:

The source and the detector trajectories are tuned to image a field-of-view (FOV) that is offset with respect to the center-of-rotation. The new reconstruction formula is derived from the Feldkamp algorithm and results in a similar three-step algorithm: projection weighting, ramp filtering, and weighted backprojection. Simulations of a Shepp Logan digital phantom were used to evaluate the new algorithm with a 10 cm-offset FOV. A real cone-beam CT image with an 8.5 cm-offset FOV was also obtained from projections of an anthropomorphic head phantom.

RESULTS:

The quality of the cone-beam CT images reconstructed using the new algorithm was similar to those using the Feldkamp algorithm which is used in conventional cone-beam CT. The real image of the head phantom exhibited comparable image quality to that of existing systems.

CONCLUSIONS:

The authors have proposed a 3D filtered-backprojection reconstruction for scanners with independent source and detector rotations that is practical and effective. This algorithm forms the basis for exploiting the scanner's unique capabilities in IGRT protocols.

PMID:
27147346
DOI:
10.1118/1.4945418
[Indexed for MEDLINE]

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