1. An energy-sensitive system, comprising: one or more processors configured to: determine spectral attenuation curves for a first basis material and a second basis material, respectively; substitute a k-edge feature in the determined spectral attenuation curves with an approximation of the determined spectral attenuation curves lacking the k-edge feature; construct a material decomposition model based on one of the determined or approximated first and second spectral attenuation curves; and decompose X-ray projection data into basis material projection data comprising first and second line integrals based, at least in part, on the model.