Computed Tomography (CT) is an imaging technique in which the attenuation of an X-ray beam that passes through a body is used to retrieve information about the inner structure of the body itself. Since it has been invented, this technique is in continuous evolution. The last frontier consists in using, for the image reconstruction, not only the beam intensity but also its energy spectrum, as the attenuation coefficient µ, from the Lambert-Beer law, is energy dependent.The main challenge in this framework is to have an energy-sensitive detector, operating in photon counting mode and, at the same time, capable to handle high fluxes.The solution adopted in this project is a hybrid pixel detector, with a 500 µm thick silicon sensor on top of a readout chip from the Medipix family that allows energy discrimination. The detector is used in edge-on geometry, with the photons impinging on the side of the detector.
This innovative configuration both improves the attenuation efficiency of silicon and provides additional energy information. This information, collected for every exposure, can be combined in a dedicated computed tomography reconstruction to provide spectral X-ray CT images.