Microtomography

Kalukin A.R., Effects of Internal Scattering on X-ray Microtomography Image Reconstruction , IEEE Transactions on Nuclear Science, vol. 44, No. 2, April 1997, pp. 142-147. 

It is shown how phase contrast X-ray microtomography can be realised with a (commercial) polychromatic X-ray microfocus tomograph provided the source size and the resolution of the detector are sufficiently small and the distance between source and detector is sufficiently large. The technique opens perspectives for high resolution tomography of light objects... 

This opens perspectives for obtaining phase contrast information in a microfocus tomographic system Recently we have developed a desktop X-ray microtomographic system [4] with a spot size of 8 micrometer (70 KeV) and equipped with a (1024) pixel CCD, lens coupled to a scintillator. The system is now commercially available [5], The setup is sketched in Figure 1 In this work we used the system to demonstrate the feasibility for phase contrast microtomography. 

For this experiment, as well as for the microtomography ( 3.2) we used the commercial desktop microtomography system Skyscan 1072 [5], the setup of which is sketched in Figure 1. For this instrument, which is designed to study relatively large objects with a diameter up to 50 mm, the source size is 8 pm, the distance source-detector is about 50 cm and the effective resolution of the detector is about 80 pm. For this system and this object, the global effective resolution a is estimated to be of the order of 50 to 100 pm [6]. 

It has been demonstrated that phase contrast microtomography is feasible with a desktop (commercial) X-ray microtomographic system The observations agree well with the theoretical predictions. This opens perspectives for high resolution microtomography of light objects. 

The X-ray microtomography has been used for a variety of applications. Most spectacular applications can be found in those areas, where three-dimensional internal structures can only be visualized non-destructively and/or in normal environmental conditions. 

A first example of application of microtomography is taken from life sciences. Here X-ray microscopy and microtomography allows to reconstruct the internal three-dimensional microstructure without any preparation and sometimes even of living objects. Fig. la shows an X-ray transmission microscopical image of bone (femoral head). Several reconstructed cross-sections are shown in Fig.lb. Fig.lc shows the three-dimensional reconstruction of this bone. 

Another application areas of microtomography are biology and agriculture. Fig.4a shows an X-ray transmission image through the tulip bulb in wet conditions. Damaged area can be found in the surface of this bulb. Fig.4b shows the reconstructed cross section with information about depth of damaged volume. 

Fig.l.Microtomography of bone shadow image (a), reconstructed cross-sections (b) and full 3-D reconstruction (c)... 

X-ray microtomography is a new development of great promise for reconstructing, displaying, and analyzing three-dimensional microstructures. Resolution of around 1 pm has been demonstrated with currently available synchrotron sources of x-rays, x-ray detectors, algorithms, and large-scale computers. The potential for microstructural research in composites, porous materials, and suspensions at this and finer scales appears to be tremendous. 

Magnetic resonance imaging, or microtomography by multinuclear magnetic resonance, is another new development that is even more exciting because it provides three-dimensional mapping of the abundance of a variety of atoms. Compositional aspects of microstructme can thereby be resolved. However, the resolution... 

Successful development of such systems will lead to foamed materials having useful stress-absorbing characteristics in addition to controlled physics properties. Although our work in this area is currently in a very early stage, prototype materials have been successfully synthesized and assessed structurally using three-dimensional (3D) X-ray microtomography. The technique offers a unique insight into the internal microstructure of cellular materials (see Fig. 3). The diameter of the mainly open cell pores varies from approximately 100 to 250 pm (the resolution of the instrument is 5 pm), with cell walls of variable thickness. 

Although, in principle it is now possible to study deformation of internal cells in foams using CT microtomography, no such research has been reported. 

Very recently, experiments using new techniques have been performed by Lodewyckx et al. [4], X-ray microtomography coupled with image analysis allows visualising dynamic adsorption of organic vapour and water vapour on activated carbon. Figure 17.3 in [4] shows profiles inside the bed at different times. It is remarkable that the fronts seem to be of constant pattern shape. 

Song SR, Jones K, Lindquist WB, Dowd BA, Sahagian DL (2001) Synchrotron X Ray Computed Microtomography Studies on vesiculated basaltic rocks. J Vole Geotherm Res 63 252-263... 

The microstructure of bread and other microporous foods can be conveniently studied by applying synchrotron radiation X-ray microtomography (X-MT) (Falcone et al., 2004a Maire et al., 2003) to centimeter- or millimeter-sized samples (Lim and Barigou, 2004). X-MT application only requires the presence of areas of morphological or mass density heterogeneity in the sample materials. The use of this technique for food microstructure detection is of recent date. It was traditionally used for the analysis of bone quality (Peyrin et al., 1998, 2000 Ritman et al., 2002). 

Falcone, P.M., Baiano, A., Zanini, F., Mancini, L., Tromba, G., Montanari, F., and Del Nobile, M. A. 2004a. A novel approach to the study of bread porous structure Phase-contrast X-ray microtomography. J. Food Sci. 69(1), 38-43. 

Peyrin, F., Salome-Pateyron, M., Nuzzo, S., Cloetens, P., Laval-Jeantet, A.M., and Baruchel, J. 2000. Perspectives in three-dimensional analysis of bone samples using synchrotron radiation microtomography. Cell Mol Biol 46(6), 1089-1102. 

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