Prior function designs for x-ray computed tomography reconstructions from limited angular views

Abstract The objectivity of three-dimensional (3D) imaging has made x-ray computed tomography (CT) an indispensable diagnostic method in clinical and industrial applications. Despite all the advances in x-ray CT imaging, high-resolution 3D reconstruction of defects and details in objects with large in-plane dimensions has been a fundamental challenge with the existing commercially available x-ray CT capabilities. An alternative scanning geometry, where an x-ray source and a detector move synchronously, irradiating a specimen at an angle from the rotation axis, has been proposed to address this challenge. To improve the reconstruction of radiography data obtained under limited angular conditions, new designs of prior (or penalty) functions are developed. The new Gaussian prior is aimed at reducing shape distortion artifacts, common in laminographic reconstructions, as well as improving edge contrast and defect detection. Prior function performance is demonstrated on a computational phantom that contains worst-case scenario defects and simulated using limited angular data CT geometry. The Gaussian prior’s superior quantitative detection of defects is shown by the line profile plots as compared to the hyperbola prior. The performance of the reconstruction algorithm with the novel prior function is further verified under real CT scan conditions using a novel microfocus x-ray CT scanning device that rotates the x-ray source and moves the detector synchronously while the x-ray source and detector stay on the same opposite side of the test specimen (inclined CT). This device allows the scanning of critical areas up to 3 m wide and potentially unlimited-length specimens with the high resolution required for the identification of manufacturing and structural defects typical of modern composite structural elements.