Note: [] J Sijbers is a Postdoctoral Fellow of the F.W.O. (Fund for
Scientific Research – Flanders, Belgium)
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exponential with the thickness of the material, is no longer valid.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.
Keywords: microtomography, beam hardening correction, bimodal energy model
