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

X-ray computed tomography (CT) reconstruction suffers from beam-hardening arte facts 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. Copyright (C) EPLA, 2019