A Reconstruction Method for Dual High-Energy CT With MeV X-Rays

Dual-energy computed tomography (DECT) allows one to obtain both density and atomic number and thus can provide information about material composition of scanned objects. In this paper, we extend a basis material decomposition method for high energy X-ray DECT used in cargo inspection. It differs from conventional DECT reconstruction methods by pair-production effect coming into play in the reconstruction. The pair-production does not happen for DECT in low energy level (lower than 1 MeV). The decomposition error of the basis material model and its applicability in the high-energy level are analyzed in this paper. A reconstruction method based on this model is proposed to reconstruct both the atomic number Z and the electron density ρe images for a high-energy DECT. The method is validated by a numerical simulation and a practical experiment on a cargo inspection system. Results show that the proposed reconstruction method is strongly grounded on physics and feasible for high-energy DECT in material discrimination, especially for cargo inspections. The advantages and limitations of the high-energy DECT, as well as possible improvements for future work are discussed in this paper.