Fast tomographic inspection of cylindrical objects

This paper presents a method for improved analysis of objects with an axial symmetry using X-ray Computed Tomography (CT). Cylindrical coordinates about an axis fixed to the object form the most natural base to check certain characteristics of objects that contain such symmetry, as often occurs with industrial parts. The sampling grid corresponds with the object, allowing for down-sampling hence reducing the reconstruction time. This is necessary for in-line applications and fast quality inspection. With algebraic reconstruction it permits the use of a pre-computed initial volume perfectly suited to fit a series of scans where same-type objects can have different positions and orientations, as often encountered in an industrial setting. Weighted back-projection can also be included when some regions are more likely subject to change, to improve stability. Building on a Cartesian grid reconstruction code, the feasibility of reusing the existing ray-tracers is checked against other researches in the same field.Comment: 13 pages, 13 figures. submitted to Journal Of Nondestructive Evaluation (https://www.springer.com/journal/10921

Characterizing analogue caldera collapse with computerized X-ray tomography

Analogue models of caldera collapse were imaged by computerized X-ray tomography (μCT). Interval μCT radiography sequences document ‘2.5D’ surface and internal model deformation in an unprecedented way, and carry the potential for a better understanding of the kinematics of various volcano-tectonic processes, of which caldera collapse is a mere illustration. A semi-automatic subsidence velocity analysis was carried out on radiographs. The developed method is a step towards the quantitative documentation of volcano-tectonic modelling that would render data interpretations immediately comparable to monitoring data available from recent deformation at natural volcanoes

Evaluation of phase correction algorithms outside the validity boundaries

In high-resolution X-ray Computed Tomography, the phase shift and refraction of X-rays can under certain circumstances become visible in the projection images, being superimposed on the attenuation images. As such, it can also become visible in the reconstructed volume. This can be beneficiary for the visualization, yet it is often considered an imaging artefact which hinders proper 3D analysis. Under normal experimental conditions, it is mathematically not possible to retrieve the phase information or the attenuation information correctly without multiple acquisitions. However, several methods exist to perform phase retrieval or phase correction, which use assumptions on the object or the imaging setup. In this presentation, the effect of a violation of these assumptions is discussed

The 'Maagdentoren' of Zichem (Belgium) : damage assessment of ferruginous sandstone by X-ray tomography

The ferruginous sandstone of the gothic “Maagdentoren” is suffering from a specific biological deterioration process triggered by perforating activities of mason bees. The damage due to these perforations causes extensive loss of material, so that a durable conservation of such degraded stone blocs becomes questionable. In order to evaluate the conservation possibilities of stone blocs damaged by perforating mason bees, an investigation of the internal structure by means of X-ray tomography was carried out. This investigation revealed that the cumulative effect of the digging work by multiple generations of mason bees may result in networks of perforations. Bioturbated sandstones were found to be most suitable for attack by mason bees because of morphological and geometrical compatibility between the original layered burrowings by marine organisms and those by the mason bees. As a conclusion the conservation is not recommended of sandstone blocs for which the load bearing capacity is endangered by the branched and layered perforations

Motion compensated micro-CT reconstruction for in-situ analysis of dynamic processes

This work presents a framework to exploit the synergy between Digital Volume Correlation ( DVC) and iterative CT reconstruction to enhance the quality of high-resolution dynamic X-ray CT (4D-mu CT) and obtain quantitative results from the acquired dataset in the form of 3D strain maps which can be directly correlated to the material properties. Furthermore, we show that the developed framework is capable of strongly reducing motion artifacts even in a dataset containing a single 360 degrees rotation