On the Fusion of Energy Resolved Scatter and Attenuation Data for Limited-View X-Ray Materials Characterization With Application to Security Screening

Motivated by the use of X-rays for security screening, we demonstrate the utility of fusing energy-resolved observations of scattered photons with traditional attenuation data for the joint recovery of electron density and photoelectric coefficient in the context of limited-view tomographic imaging scenarios. We begin by developing a physical and associated numerical model for the scatter physics used within our processing. With this model, in this paper, we propose a variational approach for recovering the two material properties. In addition to the typical data-fidelity terms, the optimization functional includes regularization for both the electron density and photoelectric coefficients. We consider an edge-preserving method in the case of electron density. We employ a nonlocal regularization scheme that improves the stability with which we can recover the photoelectric coefficient. Imaging results using Monte-Carlo simulations demonstrate both qualitative and quantitative advantages associated with supplementing traditional attenuation data with scatter observations for mapping the two material properties. The work in this paper has focused on providing an initial proof-of-concept concerning the potential utility in fusing observations of scattered and attenuated photons. Furthermore, enhancements are required to adapt this method for use in deployed security screening systems.