Artefacts in X-ray microtomography of materials

Abstract

X-ray microtomography is becoming an increasingly popular tool in the study of microstructure and failure mechanisms in biological and engineering materials, producing three-dimensional (3D) maps of the X-ray linear attenuation coefficient. Limitations of the technique are due to, for example, limited X-ray flux, use of polychromatic radiation (in laboratory systems), finite resolution, discrete sampling and X-ray scatter. These give rise to artefacts in the reconstructed image. Knowledge of these artefacts helps to distinguish them from real features and is important for optimising experimental design so as to minimise their effect on the results. To aid identification, artefacts were simulated computationally using an analytical phantom projection generator. Streak, ring, motion and beam hardening artefacts are considered as well as the results of errors in the centre of rotation and missing information in cone beam geometry. Examples of tomographic images of real materials specimens with motion and beam hardening artefacts as well as centring errors are also shown.