A combined SPECT-CT tomographic imager for breast cancer study is being developed as a large research program of Italian universities. The basic idea is to integrate the SPECT technique with a CT scanner in order to fuse the functional with the morphological information by using a high-resolution and compact gamma camera and a quasi-monochromatic X-ray system. These two dedicated systems will be assembled as a unique ring prototype, which will enable the authors to perform both the scintimammography and the X-ray tomography in the same geometrical conditions. High-intensity and tunable quasi-monochromatic X-ray beams have already been produced for mammography applications. The authors' aim is to investigate the use of this novel source for tomographic imaging of the breast.