  Recent years have seen growing interest in exploiting dual- and multi-energy
measurements in computed tomography (CT) in order to characterize material
properties as well as object shape. Material characterization is performed by
decomposing the scene into constitutive basis functions, such as Compton
scatter and photoelectric absorption functions. While well motivated
physically, the joint recovery of the spatial distribution of photoelectric and
Compton properties is severely complicated by the fact that the data are
several orders of magnitude more sensitive to Compton scatter coefficients than
to photoelectric absorption, so small errors in Compton estimates can create
large artifacts in the photoelectric estimate. To address these issues, we
propose a model-based iterative approach which uses patch-based regularization
terms to stabilize inversion of photoelectric coefficients, and solve the
resulting problem though use of computationally attractive Alternating
Direction Method of Multipliers (ADMM) solution techniques. Using simulations
and experimental data acquired on a commercial scanner, we demonstrate that the
proposed processing can lead to more stable material property estimates which
should aid materials characterization in future dual- and multi-energy CT
systems.
