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arXiv · 1808.08791

SPULTRA: Low-Dose CT Image Reconstruction with Joint Statistical and Learned Image Models

Siqi Ye·Saiprasad Ravishankar·Yong Long·Jeffrey A. Fessler
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Abstract

Low-dose CT image reconstruction has been a popular research topic in recent years. A typical reconstruction method based on post-log measurements is called penalized weighted-least squares (PWLS). Due to the underlying limitations of the post-log statistical model, the PWLS reconstruction quality is often degraded in low-dose scans. This paper investigates a shifted-Poisson (SP) model based likelihood function that uses the pre-log raw measurements that better represents the measurement statistics, together with a data-driven regularizer exploiting a Union of Learned TRAnsforms (SPULTRA). Both the SP induced data-fidelity term and the regularizer in the proposed framework are nonconvex. The proposed SPULTRA algorithm uses quadratic surrogate functions for the SP induced data-fidelity term. Each iteration involves a quadratic subproblem for updating the image, and a sparse coding and clustering subproblem that has a closed-form solution. The SPULTRA algorithm has a similar computational cost per iteration as its recent counterpart PWLS-ULTRA that uses post-log measurements, and it provides better image reconstruction quality than PWLS-ULTRA, especially in low-dose scans.

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Siqi Ye, Saiprasad Ravishankar, Yong Long, Jeffrey A. Fessler. 2019-08-12. SPULTRA: Low-Dose CT Image Reconstruction with Joint Statistical and Learned Image Models. https://doi.org/10.1109/tmi.2019.2934933

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