Quantification of the effects of grid angulation on image quality in single-grid-based phase-contrast x-ray imaging

Single-grid-based phase-contrast x-ray imaging (SG-PCXI) is a single-exposure, non-interferometric method for the simultaneous retrieval of absorption, differential phase-contrast, and dark-field images using a conventional x-ray grid; it requires minimal exposure and minimal system setup for potential medical and industrial imaging applications. However, owing to the Moiré artifact, the retrieved images are often distorted because of the inadequate sampling of the grid strips by the pixel array detector. This attribute can result in the degradation of image quality. Therefore, in this study, we propose a method for effectively removing the Moiré artifact by employing a grid angulation technique to improve image quality in SG-PCXI. We theoretically analyzed the formation of the Moiré artifact in an SG-PCXI setup and quantified the effects of grid angulation on the image quality. We conducted an experiment using a tabletop setup to verify the theoretical quantification of the effects of grid angulation on image quality. The Moiré artifact was completely removed in the retrieved images when the x-ray grid was rotated at θ = 18.2° and 26.3°, which aligned well with the theoretical quantification. Furthermore, the spatial resolution of the retrieved images improved as the grid frequency increased. Thus, the experimental results indicated that the proposed method can effectively eliminate the Moiré artifact; furthermore, it was determined that the size of the window function should be as large as possible to ensure improved image quality. The proposed method significantly improves image quality in SG-PCXI. (paper)