Realistic CT image simulation tools for laboratory based X-ray CT at UGCT

In laboratory based X-ray Computed Tomography (CT), the grey values in the resulting CT image depend on several scanning conditions such as the emitted spectrum, the response characteristics of the detector and beam filtration. Furthermore, due to beam hardening also the morphology and composition of the sample itself will have a significant influence. Therefore, to optimise scanning conditions simulations which incorporate all factors determining the imaging process are required. In this paper, two programs developed at the Centre for X-ray Tomography of the Ghent University (UGCT) are presented which allow a complete and realistic simulation of the obtained CT image

Real-time, high speed, high resolution, 4D CT at laboratory setups

Performing CT experiments on samples that are morphologically changing shape as a function of time is not straightforward, especially if the modifications happen in a short period of time and the altering structures are relatively small. These kind of experiments are challenging as large amounts of data are generated in a short amount of time and it is difficult to target the right time period where the change of interest can be observed. Additionally, hardware limitations in terms of acquisition speed and sufficient X-ray flux are problematic, especially at laboratory setups. Here we present some CT-results where a time resolution of 1sec is achieved over a period of 2 min using a combination of hard- and software that is specifically designed for high speed, high resolution, 4D CT

Modelling of X-ray tube spot size and heel effect in Arion

X-rays produced in X-ray tubes originate from a focal spot on the target material. This spot is not infinitely small, but has a finite size. This finite size of the spot will affect the radiographic projections taken during X-ray Compted tomography. In order to simulate correct radiographic projections, this finite spot size needs to be taken into account during the simulations. This can be done by modelling a two dimensional profile of the spot and use this model to convolve the simulated radiographic projections simulated with an infinitely small spot size. A second effect, the heel effect that originates in directional X-ray tubes will also have an influence on the final projections. This effect can also be modelled and this model can be used to correct the simulated projections for this effect

A LabVIEW® based generic CT scanner control software platform

UGCT, the Centre for X-ray tomography at Ghent University (Belgium) does research on X-ray tomography and its applications. This includes the development and construction of state-of-the-art CT scanners for scientific research. Because these scanners are built for very different purposes they differ considerably in their physical implementations. However, they all share common principle functionality. In this context a generic software platform was developed using LabVIEW (R) in order to provide the same interface and functionality on all scanners. This article describes the concept and features of this software, and its potential for tomography in a research setting. The core concept is to rigorously separate the abstract operation of a CT scanner from its actual physical configuration. This separation is achieved by implementing a sender-listener architecture. The advantages are that the resulting software platform is generic, scalable, highly efficient, easy to develop and to extend, and that it can be deployed on future scanners with minimal effort

Modifications of iterative reconstruction algorithms for the reduction of artefacts in high resolution X-ray computed tomography

X-ray Computed Tomography is a non destructive technique which allows for the visualization of the internal structure of complex objects. Most commonly, algorithms based on filtered backprojection are used for reconstruction of the projection data obtained with CT. However, the reconstruction can also be done using iterative reconstructions methods. These algorithms have shown promising results regarding the improvement of the image quality. An additional advantage is that these flexible algorithms can be modified in order to incorporate prior knowledge about the sample during the reconstruction, which allows for the reduction of artefacts. In this paper some of these advantages will be discussed and illustrated: the incorporation of an initial solution, the reduction of metal artefacts and the reduction of beam hardening artefacts

Qualitative comparison of several phase correction algorithms in single-image in-line X-ray phase contrast tomography

In recent years, phase contrast has gained importance in the field of X-ray imaging and more particular in high-resolution X-ray computed tomography or micro-CT. For phase propagation imaging, no additional hardware or specific setup is required, which makes the effect inherent to micro-CT where it is manifested as an edge-enhancement effect. As such, it can be beneficial for qualitative analysis of a 3D volume. Nevertheless, it induces unreal gray values and is thus often considered as an imaging artefact which hinders proper quantitative 3D analysis. Several methods exist to reduce this phase contrast effect or to retrieve the phase information from the mixed phase-and-amplitude images. In this presentation, a comparison will be made between 2 phase retrieval algorithms and 2 phase correction algorithms. Of these 2 latter, one can be performed on the reconstructed volume, which clearly facilitates the operation of phase correction