Abstract
Coherently scattered x-rays are mainly confined to a forward peaked cone, which exhibits, due to their coherence, structural information of the atomic arrangement in the sample. Coherent scattering in amorphous materials, which are of random short range order, therefore results in board diffraction ring patter, whereas crystalline substance show more confined diffraction rings or even Brag spots. X-ray diffraction computed tomography (XRDCT) reconstructs the intensities diffracted from extended objects on a square image grid and thus retrieves the local structure. A short survey is presented about what information can be extracted from diffraction experiments. Hereby a new method is proposed to use the Rietveld refinement for quantitative XRDCT. Also the possible use of XRDCT to reconstruct the spatial distribution of preferred orientation axis is suggested. An imaging system for XRDCT, consisting of a medical image intensifier tube and CCD readout system, is presented, which includes a modified beam stop for recording the intensity of the transmitted beam. Depending on the application this imaging system cam work in first generation or second generation tomography mode. Furthermore a new approach for the reconstruction of the differential coherent cross-section is proposed. It includes an absorption correction based on weighted sinograms. The introduced reconstruction strategy is elucidated by experimental result from a simple phantom. The measured data also validate the simulation program, written to study more complex phantoms under different experimental conditions. Finally possible applications in medical and material science are discussed. A design for a mammography setup using x-ray diffraction is presented.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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