Additively Manufactured Primitive Plastic Phantom for Calibration of Low-Resolution Computed Tomography Cone Beam Scanner for Additive Creation of 3D Copies using Inverse Radon Transform

Abstract

Computed Tomography (CT) and 3D reconstruction contribute significantly to reverse engineering as well as to additive manufacturing. Utilizing CT scans, surface information as well as inner details of objects of interest can be recorded non-destructively. In this work, a low-resolution computed tomography cone beam (CBCT) scanner was used to scan, reconstruct and print plastic components in order to create 3D copies. Software based calibration using an additively manufactured two layer plastic phantom containing steel ball bearings was used to detect and correct geometrical alignment errors and improve reconstruction quality. A phantom was designed to be printed additively and assembled without the help of further tools, with an axial connection to the CBCT. Corrections were applied to the two-dimensional 300x300 pixel X-ray projections before reconstruction. A reconstructed volume of 212x212x212 voxels was achieved using either the inverse-Radon-Transformation-based Feldkamp Davis Krauss (FDK) or Simultaneous Algebraic Reconstruction Technique (SART) algorithm. In an experiment, a plastic phantom was fabricated and used for misalignment correction. Two reconstructions of uncorrected and corrected projections of a 30 mm plastic cube with center bore were subsequently compared to each other in terms of density. The cube reconstructed from corrected projections had higher voxel density values and sharper slices, showing the successful fabrication and use of the plastic phantom.