K-edge spectral computed tomography with a photon counting detector and discrete reconstruction.

X-ray K-Edge Subtraction Computed Tomography (KES-CT) is based on the acquisition of two images at different energies, one below and one above the Kedge of a contrast agent. KES-CT is mainly performed at synchrotron facilities where a tunable monochromatic X-ray beam is available. Thanks to innovative Photon Counting Xray Detectors (PCXDs), it would be desirable to collect the two images in a single shot with a conventional polychromatic Xray spectrum. This approach, sometimes called spectral-CT or color-CT eliminates the risk of misregistration due to motion between consecutive acquisitions and it should allow for scans with much lower doses of contrast medium. Spectral CT is considered very promising but its practical application is being hampered by several practical issues, one of these being the charge sharing affecting the energy resolution of PCXDs. However, latest generations of PCXDs implement hardware solutions to cope with the charge sharing effects, thus allowing sharper color sensitivity. This work presents a K-edge spectral CT imaging preliminary protocol based on the Pixirad-I/PixieIII detector where discrete tomography is used to present the reconstructed slices as color images. Results show that when a solution for the charge sharing issue is considered and refined reconstruction methods are applied, accurate K-edge subtraction imaging with conventional sources can be performed.