It has been proposed that the sensitivity of breast lesion detection can be improved with phase-contrast mammographic imaging. The recently introduced clinical system by Konica-Minolta, for example, reportedly yields enhanced lesion detectability. We hypothesize that the use of an optimized x-ray spectrum will result in even better performance. To test this hypothesis, we have performed a study of several clinical spectra from Mo and W sources over a broad spectral range. In the study, we have incorporated established dose measurements from a simple breast phantom used in the digital mammography literature, which has been updated to incorporate breast density properties in addition to conventional attenuation information. Established phase-contrast imaging simulation techniques, which employed a Fresnel propagator, were used to generate edge-enhanced radiographs for analysis. In addition, detector sensitivity and tube loading parameters were incorporated into the analysis. The resulting mammography images were analyzed via measurement of object edge-enhanced contrast.