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Laboratory X-ray microtomography is a convenient method of studying the threedimensional structure of objects of different types. Modern laboratory microtomography setups allow us to carry out measurements with submicron resolution. The laboratory sources of X-ray radiations used in such setups have low intensity, so the recorded tomographic projections are noisy. This often leads to the situation when the reconstructed tomographic images are also noisy, and artifacts may appear on them (objects of a characteristic shape, which are absent in the real object). In this work, we describe the methods of noise and artifacts suppression at all stages of data processing: reducing noise in the original projection images, the inclusion of regularizing members in the tomographic reconstruction procedure, filtering of reconstructed data. The reduction of noise and artifacts on tomographic data allows not only to reconstruct the internal structure of the objects under study but also to make a step towards temporal resolution and spectral tomography on laboratory sources. [ABSTRACT FROM AUTHOR]

A new approach is proposed to solve the problem of tomographic reconstruction when scanning objects by polychromatic radiation. The application of algebraic reconstruction method, which makes it possible to take into account the spectral features of the interaction between object components and radiation, allows one to reconstruct component distribution maps. Simultaneous analysis of the thus obtained maps and the results of reconstruction using convolution and inverse projection makes it possible to interpret quantitatively the reconstruction result, despite the arising distortions. The optimization problem is solved under limitations imposed on the local composition. The reconstruction results for synthetic projections are discussed. [ABSTRACT FROM AUTHOR]

First experimental results of fluorescence microtomography with 6-[micro]m resolution obtained at ESRF, Grenoble, France, are described. The setup comprises high-quality optics (monochromator, mirror, focusing lenses) coupled to the high-energy/brilliance/coherence of the ID 22 undulator beamline. The tomographic setup allows precise measurements in the 'pencil-beam' geometry. The image reconstruction is based on a modification of the algebraic reconstruction method but includes simplifications of the model. The quality and precision of the two-dimensional reconstructed elemental images of a phantom sample are encouraging. The method will be further refined and applied for the analysis of more complex inhomogeneous samples. Index Terms--Algebraic reconstruction method, synchrotron radiation, X-ray fluorescence microtomography, X-ray microprobe.

The response signal collection functions in a confocal setup of the X-ray fluorescence (XRF) tomography have been modeled for a polycapillary collimator and a multichannel collimator fabricated by means of microelectronic technology (MT). The dimensions of the effective collection region for the two types of collimators are compared. For the MT-fabricated device, a fraction of X-ray photons transmitted due to the total external reflection from channel walls has been evaluated. It is shown that, for a proper choice of parameters, the contribution of these photons to the collection function is negligibly small. [ABSTRACT FROM AUTHOR]

Abstract: Recently, there has been a renewed interest for fluorescence spectroscopy, as provided by modern setups which allow 2D and 3D imaging of elemental distributions. Two directions are currently under development: the SR-based fluorescence tomography in polar scanning geometry, provided by the new generation of X-ray microprobes and the confocal scanning geometry, which can be fielded in both SR and laboratory environments. The new probes bring forth a new age in fluorescence spectrometry: high resolution, high intensity and high sensitivity which allow 3D elemental mapping of volumes. The major task now is the development of these complex tools into fully quantitative probes, reproducible and straightforward for general use. In this work we analyze two X-ray fluorescence microtomography techniques: an apparatus tomography using a confocal collimator for the data collection and a standard first generation Computed Tomography (CT) in the parallel scanning scheme. We calculate the deposited dose (amount of energy deposited and distributed in the sample during the data collection time) and find the conditions for the choice of the tomography scheme. [Copyright &y& Elsevier]

The capabilities and limitations of wavelet analysis are demonstrated for the illustrative case of two practial applications: investigation of magneto-tunneling signals and the extended x-ray absorption fine structure (EXAFS) of uranium. A brief introduction to wavelet analysis is given. The term “window size” of the mother wavelet function is defined; this concept underlies one of the ideas for a criterion of optimal choice of the mother wavelet function. The capabilities of a software package developed by the authors are demonstrated; this software was used for all the calculations done in the course of this study. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Different reconstruction techniques are used to reconstruct the distribution of the physical characteristics, describing a sample under investigation, from a set of tomographic projections. We present a technique for the evaluation of the reconstruction quality. The technique is based on the comparison of two images (phantom and reconstructed image) by means of the correlation coefficient and of the mean square error between them. In parallel, the correlation coefficient and mean square error are calculated for the wavelet transforms of the phantom and reconstructed images. The scales for the wavelet transform are chosen in agreement with the major geometric parameters of the phantom. Then the correlation coefficient of the wavelet transform with the chosen scale yields an evaluation of the quality of the phantom parameters reconstruction. The accuracy of the parameters reconstruction is determined by the mean square error for the selected scale. The phantom used for the analysis is a medium with randomly distributed grains. The distribution is characterized by two parameters: grain size and grain density (average number of grains per unit area). The parameters are used as the scales for the wavelet transform calculation. We make a comparison of the Algebraic Reconstruction Technique (ART) and the Filtered Back Projection Algorithm. [Copyright &y& Elsevier]