(Sunday, 7/12/2020) [Eastern Time (GMT-4)]
Room: AAPM ePoster Library
Purpose: conventional filtered-backprojection (FBP) method applies several designed weightings to process reconstruction of circular scans with non-uniform data redundancy. However, we found that derivative backprojection filtration (DBF) reconstruction using the same weightings suffer unexpected streaking artifacts along the direction of the Hilbert transform. This work aims to explore the cause of this artifacts and propose corresponding accurate CT reconstruction via DBF
Methods: after introducing designed weightings for non-uniform data redundancy, the DBF reconstruction formula could be decomposed into three parts, in which the raw projections, signum function and weightings are differentiated respectively. We found that the streaking artifacts originate from the derivative of weightings truncated by the signum function, and further investigation reveals that the error of discretization contributes to these directional artifacts since the artifacts gradually disappear as the projections increase. Based on the analysis above, we extract the streaking artifacts from the raw images in three specific scan modes, i.e., half fan scan, short scan and multi-source scan. Different scan modes present streaking artifacts with different patterns due to the mode-specific weightings, and mode-specific correction methods are then proposed to achieve accurate reconstruction according to the characteristics of each scan mode.
Results: evaluate the proposed method via both simulation and phantom studies, with short scan, half fan scan and multi-source scan in the investigation scope. Streaking artifacts are effectively removed in the Shepp-Logan phantom results, and difference images which refer to full fan full scan image as ground truth only present noise pattern, indicating improved numerical accuracy. Phantom studies demonstrated that the proposed method has no adverse impact on the spatial resolution as evidenced by the non-degraded visibility of line-pairs.
Conclusion: propose accurate CT reconstruction via DBF for circular scans with non-uniform data redundancy, which improves numerical accuracy without reducing the spatial resolution.
Funding Support, Disclosures, and Conflict of Interest: National Natural Science Foundation of China (Grant No. 81671681) The Ministry of Science and Technology of China Key Research and Development Projects (Grant No. 2016YFC0101400) The Fundamental Research Funds for the Central Universities (Grant No. WK2030040089).
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