State-of-the-art setups for K-edge imaging

Spectral imaging is an emerging area of X-ray imaging that includes all the techniques which exploit the energy-dependent absorption properties of the matter to either provide quantitative information about the scanned object or to discriminate different materials. Though the potentials of spectral imaging are well known for over many years, the interest on spectral techniques is rapidly increasing only in recent years due to the development and widespread of dedicated acquisition systems able to acquire simultaneous (or nearly simultaneous) X-ray images at different energies. In this context, the development of energy resolving X-ray photon counting detectors (XPCDs) and the increasing availability of synchrotron radiation can provide interesting solutions for spectral imaging applications such as e.g. the K-edge technique. This thesis presents the implementation and the optimization of two state-of-the art acquisition systems suitable for spectral imaging applications with particular interest on the K-edge technique. The first system is an acquisition setup for spectral Computed Tomography (CT) made by coupling a polychromatic source with an energy resolving XPCD implementing two energy thresholds. The work carried out with this setup concerned the thorough characterization of an innovative XPCD featuring a sharp energy resolution, the design of a dedicated image processing procedure to achieve high quality CT images and the development of an automated procedure to produce accurate 3D maps of a K-edge element within a sample. Moreover, to allow further optimization studies, a simulator able to reproduce X-ray images with energy resolving XPCDs has been modeled, developed and validated. The last part of this thesis presents the development and the implementation of an acquisition setup for spectral imaging at synchrotron sources based on bent-Laue crystal optics. The results achieved with a prototype setup optimized for energies around 20 keV are presented, the future developments of the technique are discussed.