Sample preparation for element analysis of many biological tissues is difficult to achieve and prone to introduce contamination. Using x-ray fluorescence element microtomography (XFEMT) the element distribution on a virtual section across the sample can be determined with a resolution in the micrometer range. Fluorescence microtomograms of two plant samples are shown, demonstrating the possibility to map physiologically relevant ions, trace elements, and heavy metal pollutants at the cellular level. Attenuation effects inside the plant are corrected by a self-consistent tomographic reconstruction technique.
In the field of hard X-ray microtomography one goal IS the enhancement of resolution Several ways can be followed to obtain this objective. One possibility is the use of high-resolution X-ray films or detector screens coupled with a microscope optical system. The limitation of resolution is either given by the grain size of the X-ray film or the point spread function of the scintillator screen and the diffraction limit of the microscope. Tomography resolution can also be improved by magnified imaging of the object on the detector system. The appearance of X-ray lenses, such as Fresnel zone-plates (FZP), Bragg-Fresnel lenses and recently compound refractive lenses (CRL) opened a large field for magnified imaging, similar to glass lenses for visible light. These new optical elements are already employed for X-ray imaging and can also be used for magnified microtomography. They have the potential of improving the resolution to a few hundred nanometers, which would overcome the resolution limits of current detectors. First tomography experiments with compound refractive lenses using a monochromatic beam as well as a so-called ""pink"" beam with a large energy bandwidth (DE/E = 10-2 compared to DE/E = 10-4 for a monochromatic beam) give promising results. 23-64
from different complex materials with scanning microbeam SAXS/WAXS. Results from the imaging of nanostructural parameters such as shape, size and orientation of nanoscale inhomogeneities in bone and other hierarchical biocomposites are presented. Moreover, a unique combination of in-situ bending deformation with X-ray nanobeam scanning is demonstrated for single carbon fibres. One of the most recent therapeutic strategies for the reconstruction of damaged large bony segments includes the tissue engineering approach. It takes advantage of the patient's own cells, which are isolated, expanded in vitro, loaded onto a bioceramic scaffold and reimplanted into the lesion site. Bone marrow stromal cells (BMSC) are the most commonly used cell type.A structural characterization of the engineered bone is largely desirable. An important point is to evaluate if the BMSC extracellular matrix deposition on a bioceramic scaffold recapitulates the ontogeny of the natural bone development. Moreover the investigation of the interaction between the newly deposited bone and the scaffold results particularly interesting. Indeed the chemistry and the geometry of the scaffold used to deliver BMSC in the lesion site determine spatial organization of the new bone and the bone-biomaterial integration.We investigated for the first time the local interaction between the newly formed mineral crystals in the engineered bone and the biomaterial by means of microdiffraction, using a set-up based on an X-ray waveguide. We demonstrated that the newly formed bone is well organized inside the scaffold pore, following the growth model of natural bone, and that there is a good adhesion with the scaffold. Combining Wide Angle (WAXS) and Small Angle (SAXS) X-ray Scattering with high spatial resolution, we were able to determine the orientation of the crystallographic c-axis inside the bone grains, and the orientation of the mineral crystals and collagen micro-fibrils with respect to the scaffold. Moreover from a quantitative analysis of both the SAXS and WAXS patterns the grain size appears to be compatible with the model for early stage mineralization. Polychromatic x-ray microdiffraction combined with differential aperture microscopy is a powerful new method for studying the local crystallographic structure of materials. This approach extends singlecrystal methods to virtually all materials including materials characterized by heterogeneity at the atomic and mesoscopic length scales. Defects such as grain boundaries, surfaces, precipitates, second phases, strain, dislocations, vacancies, interstitials, site substitutions and other disruptions of perfect periodicity all have signatures best studied using single crystal methods. Here we describe emerging x-ray microbeam techniques that exploit "single-crystal like" x-ray diffraction measurements on subgrains in typical polycrystalline materials. We show how polychromatic and tunable monochromatic measurements on small sample volumes can bring single-crystal techniques to real materials and reveal thei...
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