Abstract
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.
Highlights
Limited-angle iterative reconstruction (LAIR) is an image reconstruction method developed for to compensate incomplete data acquisition [1]
Using the proposed LAIR technique, we can significantly improve the image quality (IQ) so that there are negligible differences in IQ between the limited angle (LA) and full-scan computed tomography (CT) modes
Simulated LA sinogram and (c) context encoder (CE) inpainted sinogram the specific X-ray tracing with unit of mm 1
Summary
Limited-angle iterative reconstruction (LAIR) is an image reconstruction method developed for to compensate incomplete data acquisition [1]. LAIR provides new acquisition flexibility and innovative instrument design that is not restricted by the size of the object [2] and mitigates the high radiation dose required for computed tomography (CT) imaging [3]. Three options exist toward managing this issue: (1) reduced X-ray exposure, (2) sparse reconstruction (extend sampling interval from a projection with full-coverage) and (3) limited-angle (LA) reconstruction (new acquisition flexibility and innovative instrument design, for example, the rotation-type tomosynthesis system). The frequency spectrum is truncated, resulting in artifacts and difficulties in obtaining high-quality reconstructed images. This problem arises when a limited angular range is necessary for various reasons; it results from intensity inhomogeneity and streaking artifacts in the image domain
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