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

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

Modelling scattering contributions in X-ray micro-CT scanners with variable geometry

It is commonly known that scattered X-rays (both Compton- and Rayleigh scattering) produce a disturbing contribution to the projection images taken during a CT-scan. In medical CT a scatter-grid and collimators are used to decrease the contribution of scatter. In high resolution micro-CT scanners such as those at UGCT, the "Centre for X-ray Tomography" of the Ghent University, this approach is not possible because of the inherent structure of the used detector systems (e.g. flatpanels) and the highly variable geometry of the scanners. At UGCT a wide variety of samples is scanned, requiring different geometries. Very small samples are positioned close to the X-ray source, while larger samples have to be positioned close to the detector. The samples also have a wide range of densities, from organic material, such as apples, to geological stones and metals. For several reasons it is important to determine the specific amount of scattered X-rays that reach the detector in micro-CT. This amount is dependent on the distance between the object and the detector, the composition and size of the sample… . Also the geometry of the scanner and the kind of X-ray source (pencil beam, parallel beam or cone-beam) can have a relevant effect. As such, every different sample in its optimal geometry will cause a different amount of scattered photons reaching the detector plane. To study the characteristics of scattered radiation, the Monte Carlo based simulation program BEAMnrc is used . BEAMnrc is based on the EGS-code developed for coupled transport of photons and electrons . In BEAMnrc each photon can be ‘followed’ during the complete simulation. For each photon tallied at the detector plane one can determine whether this photon has scattered in the sample or not, which yields the number of scattered photons, next to the number of unscattered photons. The final goals of this research are to add a scatter-tool in our set-up optimizer and to be able to correct projection images for the scattering contribution. The used methodology and obtained results of this work will be presented

Optimization of scanner parameters for dual energy micro-CT

Two materials of different composition can have very similar grey values in an X-ray Computed Tomography (CT). This is because X-ray CT uses polychromatic sources in combination with energy-integrating detectors and the materials have a mass attenuation coefficient that is dependent on composition and photon energy. A distinction between different materials with similar grey values can be made by combining information from scans performed with different spectra, which can be achieved by varying the tube voltage and filtration. However, the polychromatic behaviour of laboratory based X-ray CT complicates the choice of the appropriate scanning conditions for such dual energy methods. Here, the programme Arion, for simulating realistic radiographic projections is used to determine optimal scanning parameters

Elements and principles of a strategic communication approach to health promotion in a multicultural context

Health communication projects are a key instrument in disease prevention and alleviation, as well as in health promotion and education in a broader sense, but only to the extent that such efforts are grounded in a thorough understanding of the general context of the health issue concerned and if developed in concert with other instruments and aspects of health care. Such a complex undertaking calls for a strategic and integrated approach involving many different types of expertise and research. This article briefly introduces a broad model for strategic health communication planning that is firmly grounded in the issue of health care at large. The focus then narrows to a discussion of certain aspects of health communication planning in a multicultural environment. To this end, some concrete suggestions are provided to assist policymakers, fieldworkers and researchers in evaluating or setting up effective communications in a health context

Posters, billboards and grassroots media relating to TB and AIDS in the Free State and Lesotho

This contribution examines the TB- and HIV/AIDS-related health promotion materials currently in use in the Free State (South Africa) and in Lesotho. It first considersthe cultural implications of choosing various visual and verbal design elements in a health-related message. It then analyses a number of health promotion posters on the basis of research findings and the general principles of message design in a multicultural context. Finally, a visual essay approach is taken, commenting on the roadside billboards and alternative health promotion media encountered in the Free State and Lesotho

High-resolution imaging of kidney vascular corrosion casts with nano-CT

A vascular corrosion cast of an entire mouse kidney was scanned with a modular multiresolution X-ray nanotomography system. Using an isotropic voxel pitch of 0.5 mu m, capillary systems such as the vasa recta, peritubular capillaries and glomeruli were clearly resolved. This represents a considerable improvement over corrosion casts scanned with microcomputed tomography systems. The resolving power of this system was clearly demonstrated by the unique observation of a dense, subcapsular mat of capillaries enveloping the entire outer surface of the cortical region. Resolution of glomerular capillaries was comparable to similar models derived from laser scanning confocal microscopy. The high-resolution, large field of view and the three-dimensional nature of the resulting data opens new possibilities for the use of corrosion casting in research