The present technology relates to the generation of a CT image under an arbitrary energy spectrum based on the results of a dual energy scan. In certain embodiments, a dual energy scan is conducted of an object and material basis decomposition is used to decompose the scanned object into two basis materials with known attenuation properties resulting in material density images. Along with knowledge of other imaging system information, forward projection is done under an arbitrary kV spectrum to generate an image as if the scanned object was scanned under this different kV spectrum. This prevents users from conducting unnecessary additional scans.