Combining dual energy and multi-positional computed tomography for enhanced metal artefact reduction

Industrial X-ray computed tomography (CT) is a versatile non-destructive imaging technique used to inspect the internal structure of materials and components. However, often metal artefacts deteriorate the quality of reconstructed volumes, impeding their analysis. As a consequence, various approaches for artefact reduction have been developed. Several of these combine CT scans obtained with two different X-ray spectra. This so-called dual energy CT successfully reduces beam-hardening artefacts by leveraging the additional information provided through the different spectra. It fails, though, when photon starvation occurs. In contrast, multi-positional CT uses complementary information from scans with different object orientations to mitigate these artefacts. However, it only succeeds if they don’t impair the same voxels in both reconstructed volumes. This paper presents a combination of dual energy and multi-positional CT, aiming to use the advantages of both methods to compensate their respective limitations. The presented proof-of-concept study evaluates simulations and measurements, both qualitatively and quantitatively. It shows that the fusion of four volumes, acquired with two different X-ray spectra and two different object orientations, yields superior artefact reduction.