Add to ORKGWe have tested the imaging capabilities of a GaAs pixel detector using a test object developed for quality control purposes in mammography and a dedicated X-ray imaging system. The response of this detector under the same irradiation conditions has also been simulated by the EGS4 code and a comparison with an intensifying screen+film digitized image has been made. Our GaAs detector is able to perform a measurement of low-contrast details, with a minimum contrast lower than typically detected by standard mammographic film+screen system, in the same conditions of clinical routine, and this should allow for an earlier diagnosis of the breast tumor masses