Improved tomographic reconstructions using adaptive time-dependent intensity normalization

Abstract

The first processing step in synchrotron-based micro-tomography is the normalization of the projection images against the background, also referred to as a white field. Owing to time-dependent variations in illumination and defects in detection sensitivity, the white field is different from the projection background. In this case standard normalization methods introduce ring and wave artefacts into the resulting three-dimensional reconstruction. In this paper the authors propose a new adaptive technique accounting for these variations and allowing one to obtain cleaner normalized data and to suppress ring and wave artefacts. The background is modelled by the product of two timedependent terms representing the illumination and detection stages. These terms are written as unknown functions, one scaled and shifted along a fixed direction (describing the illumination term) and one translated by an unknown two-dimensional vector (describing the detection term). The proposed method is applied to two sets (a stem Salix variegata and a zebrafish Danio rerio) acquired at the parallel beam of the micro-tomography station 2-BM at the Advanced Photon Source showing significant reductions in both ring and wave artefacts. In principle the method could be used to correct for time-dependent phenomena that affect other tomographic imaging geometries such as cone beam laboratory X-ray computed tomography.

The Imaging of Dynamic Multiphase Fluid Flow Using Synchrotron-Based X-ray Microtomography at Reservoir Conditions

“…The image time series was reconstructed using a filtered back-projection algorithm (Titarenko et al 2010). The reconstruction centre was found for the first and last image in the sequence and linearly interpolated between these two values for the others.…”

Yield behavior beneath hardness indentations in ductile metals, measured by three-dimensional computed X-ray tomography and digital volume correlation

“…In the back projection reconstruction of the synchrotron tomographs [30], a combined Fourier-wavelet algorithm [31] was used to suppress ring artefacts (for more details see [31]). These arise from instrument features such as defective pixels in the scintillator; if not adequately supressed they can significantly increase noise in the DVC analysis as they do not displace with the material.…”

On compression and damage evolution in PTFE and PEEK

“…The PCO 4000 camera (with 4008×2672 pixels) imaged a scintillation screen capturing 3001 radiographic projections during a 180° rotation of the sample about the impact axis. A filtered back projection algorithm was used to reconstruct the 3D volume representing X-ray attenuation of the sample with a voxel size of 3.6 μm, allowing visualization of the sample surfaces including internal voids [10]. Figure 2 shows three illustrative sequences and analyses taken from high-speed photography of impacts of PEEK and PTFE.…”