A model-based correction method for beam hardening artefacts in X-ray microtomography

Abstract

In micro computer tomography (μCT) and medical CT, X-ray sources are polychromatic. Because of this polychromaticity, Beer's law, which states that the ratio of the attenuated and incoming X-ray beam is exponential with the thickness of the material, is no longer valid. This leads to quantitative and visual errors in the reconstructed images, e.g. cupping and streak artefacts. This paper describes a correction scheme for these artefacts using a bimodal energy model for the source-detector energy spectrum. In essence, this correction procedure is a linearization technique based on a physical model. Results are obtained for different test objects made of combinations of plexiglas, bone, water, and aluminium. They demonstrate the effectiveness of the bimodal model correcting for the beam hardening artefact in two-, and multi-component systems.