Investigation of a one-step spectral CT reconstruction algorithm for direct inversion into basis material images

Taly Gilat Schmidt; Emil Y. Sidky

doi:10.1117/12.2082057

18 March 2015 Investigation of a one-step spectral CT reconstruction algorithm for direct inversion into basis material images

Taly Gilat Schmidt, Emil Y. Sidky

Author Affiliations +

Proceedings Volume 9412, Medical Imaging 2015: Physics of Medical Imaging; 94124Y (2015) https://doi.org/10.1117/12.2082057
Event: SPIE Medical Imaging, 2015, Orlando, Florida, United States

Abstract

Photon-counting detectors with pulse-height analysis have shown promise for improved spectral CT imaging. This study investigated a novel spectral CT reconstruction method that directly estimates basis-material images from the measured energy-bin data (i.e., ‘one-step’ reconstruction). The proposed algorithm can incorporate constraints to stabilize the reconstruction and potentially reduce noise. The algorithm minimizes the error between the measured energy-bin data and the data estimated from the reconstructed basis images. A total variation (TV) constraint was also investigated for additional noise reduction. The proposed one-step algorithm was applied to simulated data of an anthropomorphic phantom with heterogeneous tissue composition. Reconstructed water, bone, and gadolinium basis images were compared for the proposed one-step algorithm and the conventional ‘two-step’ method of decomposition followed by reconstruction. The unconstrained algorithm provided a 30% to 60% reduction in noise standard deviation compared to the two-step algorithm. The fTV =0.8 constraint provided a small reduction in noise (∼ 1%) compared to the unconstrained reconstruction. Images reconstructed with the fTV =0.5 constraint demonstrated 77% to 94% standard deviation reduction compared to the two-step reconstruction, however with increased blurring. There were no significant differences in the mean values reconstructed by the investigated algorithms. Overall, the proposed one-step spectral CT reconstruction algorithm provided three-material-decomposition basis images with reduced noise compared to the conventional two-step approach. When using a moderate TV constraint factor (fTV = 0.8), a 30%-60% reduction in noise standard deviation was achieved while preserving the edge profile for this simulated phantom.

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Taly Gilat Schmidt and Emil Y. Sidky "Investigation of a one-step spectral CT reconstruction algorithm for direct inversion into basis material images", Proc. SPIE 9412, Medical Imaging 2015: Physics of Medical Imaging, 94124Y (18 March 2015); https://doi.org/10.1117/12.2082057

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