Component separation for spectral X-ray imaging using the hybrid pixel camera XPAD3

Hybrid pixel cameras are new devices for which photon counting replaces charge integration, which have the capability to acquire spectral information on the counted photons. This ability is of uppermost importance for the development of new polychromatic X-ray imaging for which one goal is to separate images in several components of physical and biological interest. For instance, the photoelectric and Compton contributions can be separated while several contrast agents can be simultaneously localized. In this paper, we investigate the capability to perform component separation by using the newly developed hybrid pixel camera XPAD3 incorporated in the microCT demonstrator PIXSCAN. Several experiments have been led on data simulated analytically and by Monte Carlo, showing the great interest of component separation to enhance the contrast of materials when compared to classical X-ray data processing in microCT, and to cancel beam hardening artifacts. Results obtained on real data acquired with PIXSCAN on a phantom including Aluminium, water and Yttrium, the latter being treated as a contrast agent, show that the photoelectric, Compton and Yttrium components can be clearly separated and that each of them carries information allowing for the identification of different structures within the phantom.