Signal-to-thickness calibration and pixel-wise interpolation for beam-hardening artefact reduction in microCT

¹ Chair of Biomedical Physics, Department of Physics and Munich School of BioEngineering, Technical University of Munich - 85748 Garching, Germany
² MITOS GmbH - 85748 Garching, Germany
³ Department of Diagnostic and Interventional Radiology, Klinikum rechts der Isar, Technical University of Munich 81675 München, Germany

^(a) nikolai.gustschin@tum.de

Received: 15 November 2018
Accepted: 30 January 2019

Abstract

X-ray computed tomography (CT) reconstruction suffers from beam-hardening artefacts caused by the polychromaticity of virtually all lab-based X-ray sources. A method to correct for beam-hardening is a direct, pixel-wise signal-to-thickness calibration (STC). We compare reconstructions of conventionally flat-field corrected as well as STC preprocessed measurements of various samples performed on a commercial microCT device based on a flat-panel detector. We show that a good estimate between the transmission signal and the respective material thickness can be given by multiple exponential functions. We further compare the exponential interpolation approach to a hyperbolic model, which reduces the number of necessary calibration measurements significantly. Our method shows that typical beam-hardening artefacts like cupping and filling can be almost completely suppressed and a significant contrast increase is gained. The method can be applied with little additional calibration and computation effort and allows shorter acquisition times since beam filtration can be reduced or omitted.