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28 February 2006 Conjugate backprojection approach for cone beam artifact reduction
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With the introduction of volumetric computed tomography (VCT), many studies have been conducted on the cone beam reconstruction algorithms. Majority of the research efforts was devoted to the reduction of cone beam artifacts by designing special weighting functions that treat the projection samples differently based on their cone angles. The selection of weighting function can be quite complex due to the cone beam helical geometry and is often designed through trial-and-error. In this paper, we present a conjugate backprojection approach (CBA) that is capable of significantly reducing cone beam artifacts without the application of a pre-backprojection weighting function. Our approach utilizes CBA operation which simultaneously backprojects and interpolates conjugate sampling pairs. Unlike the conventional backprojection, the final backprojected value depends not only on the distance of these samples to the point-of-intersection, but also on the cone angles of these samples. Consequently, optimization can be performed on a pixel by pixel basis and is independent of the acquisition protocols, such as helical pitches or acquisition modes. The proposed approach is applicable to cone beam helical as well as step-and-shoot acquisitions. Extensive computer simulation and phantom experiments were conducted to demonstrate the efficacy of our approach. Results have shown that the proposed approach significantly reduces the cone beam artifacts.
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Jiang Hsieh and Xiangyang Tang "Conjugate backprojection approach for cone beam artifact reduction", Proc. SPIE 6142, Medical Imaging 2006: Physics of Medical Imaging, 614225 (28 February 2006);

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