Development of Limited-Angle Iterative Reconstruction Algorithms with Context Encoder-Based Sinogram Completion for Micro-CT Applications

• Published in: Sensors (Basel, Switzerland) Switzerland), 2018-12, Vol.18 (12), p.4458
• Main Authors: Jin, Shih-Chun, Hsieh, Chia-Jui, Chen, Jyh-Cheng, Tu, Shih-Huan, Chen, Ya-Chen, Hsiao, Tzu-Chien, Liu, Angela, Chou, Wen-Hsiang, Chu, Woei-Chyn, Kuo, Chih-Wei
• Format: Article
• Language: English
• Subjects: context encoder (CE); generative adversarial network (GAN); limited-angle iterative reconstruction (LAIR)
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s18124458

Limited-angle iterative reconstruction (LAIR) reduces the radiation dose required for computed tomography (CT) imaging by decreasing the range of the projection angle. We developed an image-quality-based stopping-criteria method with a flexible and innovative instrument design that, when combined with LAIR, provides the image quality of a conventional CT system. This study describes the construction of different scan acquisition protocols for micro-CT system applications. Fully-sampled Feldkamp (FDK)-reconstructed images were used as references for comparison to assess the image quality produced by these tested protocols. The insufficient portions of a sinogram were inpainted by applying a context encoder (CE), a type of generative adversarial network, to the LAIR process. The context image was passed through an encoder to identify features that were connected to the decoder using a channel-wise fully-connected layer. Our results evidence the excellent performance of this novel approach. Even when we reduce the radiation dose by 1/4, the iterative-based LAIR improved the full-width half-maximum, contrast-to-noise and signal-to-noise ratios by 20% to 40% compared to a fully-sampled FDK-based reconstruction. Our data support that this CE-based sinogram completion method enhances the efficacy and efficiency of LAIR and that would allow feasibility of limited angle reconstruction.