X-ray computed tomography (CT) is a non-destructive technique allowing the visualization of sample internal structure. A medical CT scanner consists in an X-ray source and a detector, which face each other and rotate around the sample. Bi-dimensional radiographic projections are acquired at various angles from 0° to 360° and then processed by a mathematical algorithm (i.e., image reconstruction) in order to obtain a 3D visualization of the object. Different types of image reconstructions exist, including the widely used filtered backprojection that requires little computational resources but produces less qualitatively accurate images, and iterative reconstruction, based on time consuming and numerically intensive algorithm but providing better images quality (Bushberg et al., 2012).The images are displayed in a gray scale related to the X-ray attenuation by the sample materials (Rizescu et al., 2001).Initially, this technology was developed for medical imaging, but its potential for other domains was rapidly understood (Mees et al., 2003).This paper explores a specific CT methodology, called dual-energy CT scanning (DECT), elaborated for the first time in the seventies by Alvarez and Makovski (1976). The technique consists in imaging objects with two different X-ray spectra and in combining the results to achieve various objectives, including one allowing the discrimination and identification of materials based on their density and elemental composition. From a physical perspective, DECT exploits the energy dependence of photoelectric absorption and Compton scattering

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-X-ray computed tomography is becoming a common technique for the structural analysis of samples of cultural relevance, providing luthiers, art historians, conservators and restorators with a unique tool for the characterization of musical instruments. Synchrotron-radiation phase-contrast microtomography is an ideal technique for the non-destructive 3D analysis of samples where small lowabsorbing details such as larvae and eggs can be detected. We report results from the first feasibility studies performed at the Elettra synchrotron laboratory, where the 1494 organ by Lorenzo Gusnasco da Pavia has been studied. Together with important information about the structural conditions, the presence of xylophages could be detected and characterized.

In this work related to the use of a commercial medical CT scanner for the non-destructive analysis of highly attenuating materials (mineral samples), the effect of backprojection techniques and truncation artifacts corrections were explored. For small ROIs, the CT couch interferes significantly in images of small samples (few centimeters). An iterative reconstruction algorithm (OSC-TV) was used to perform reconstructions from uncorrected raw projection data made available through a collaboration with the CT vendor, who provided binaries and methods to remove low-level, proprietary data corrections (for beam hardening). The OSC-TV algorithm is customizable, allowing for the use of different forward-projection and backprojection techniques. Reconstruction parameters were tuned by performing simulations in a virtual phantom involving highly attenuating materials. Strategies to reconstruct small ROIs were also explored, with the objective of reducing truncation artifacts. Three samples were scanned to compare a ray-driven backprojection and a voxel-driven backprojection technique based on bilinear interpolation. The voxel-driven approach led to better results in terms of noise and reconstruction artifacts. An iterative ROI reconstruction technique was used to reconstruct small ROIs. This technique allows obtaining a sinogram with the projections of the ROI only. With that, truncation artifacts were reduced, which led to images with less blurring.