1. A method for determining an optimal monochromatic energy for all or a portion of a simulated monochromatic image, the method comprising: accessing at least a first image acquired using a first polychromatic spectrum and a second image acquired using a second polychromatic spectrum; generating material density maps for at least two materials using the first image and the second image; generating a plurality of simulated monochromatic images using the material density maps, wherein each simulated monochromatic image is at a different monochromatic energy; generating a respective histogram for each simulated monochromatic image, wherein each histogram is characterized by a respective dispersion; for each histogram, deriving a quantitative metric characterizing the respective dispersion; evaluating the quantitative metrics of the histograms to determine the histogram where dispersion is minimized; and identifying the monochromatic energy corresponding to the histogram where dispersion is minimized as a target monochromatic energy at which homogeneous tissue responses have the least variation.