Estimating 0th and 1st moments in C-arm CT data for extrapolating truncated projections

Jared Starman; Norbert Pelc; Norbert Strobel; Rebecca Fahrig

doi:10.1117/12.596041

29 April 2005 Estimating 0^th and 1^st moments in C-arm CT data for extrapolating truncated projections

Jared Starman, Norbert Pelc, Norbert Strobel, Rebecca Fahrig

Proceedings Volume 5747, Medical Imaging 2005: Image Processing; (2005) https://doi.org/10.1117/12.596041
Event: Medical Imaging, 2005, San Diego, California, United States

Abstract

C-Arm CT systems suffer from artifacts due to truncated projections caused by a finite detector size. One method used to mitigate the truncation artifacts is projection extrapolation without a priori knowledge. This work focuses on estimating the 0^th and 1^st moments of an image, which can be used to extrapolate a set of truncated projections. If some projections are not truncated, then accurate estimation of the moments can be achieved using only those projections. The more difficult case arises when all projections are truncated by some amount. For this case we make simplifying assumptions and fit the truncated projections with elliptical profiles. From this fit, we estimate the 0^th and 1^st moments of the original image. These estimated moments are then used to perform an extrapolation of the truncated projections, where each projection meets a constraint based on the 0^th and 1^st moments (moment extrapolation). This work focuses on how accurate moment estimates must be for moment extrapolation to be effective. The algorithm was tested on simulated and real data for the head, thorax, and abdomen, and those results were compared to symmetric mirroring by Ohnesorge et al., another extrapolation technique that requires no a priori knowledge. Overall, moment estimation and mass extrapolation alleviates a large amount of image artifact, and can improve on other extrapolation techniques. For the real CT head and abdominal data, the average reconstruction error for mass extrapolation was 48% less than the reconstruction error for symmetric mirroring.

Citation Download Citation

Jared Starman, Norbert Pelc, Norbert Strobel, and Rebecca Fahrig "Estimating 0^th and 1^st moments in C-arm CT data for extrapolating truncated projections", Proc. SPIE 5747, Medical Imaging 2005: Image Processing, (29 April 2005); https://doi.org/10.1117/12.596041

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