1. An X-ray imaging system ( 10 ) comprising: an X-ray image acquisition device ( 12 ) with an X-ray source ( 14 ) and an X-ray detector ( 16 ); a processing unit ( 18 ); and an interface unit ( 20 ); wherein the X-ray image acquisition ( 12 ) device is adapted to acquire first image data with first image acquisition parameters; wherein the first image parameters are adapted to a first radiation spectrum of a dual energy mode; and wherein the X-ray image acquisition device is adapted to perform the first image acquisition with a low X-ray dosage of a pre-scan; and wherein the X-ray image acquisition device is adapted to acquire second image data with second image acquisition parameters; wherein the second image parameters are adapted to a second radiation spectrum of the dual energy mode; and wherein the X-ray image acquisition device is adapted to perform the second image acquisition with a higher X-ray dosage than the first image acquisition, and wherein the second image acquisition is a Mammography scan; wherein the processing unit ( 18 ) is adapted to perform a dual energy basis material decomposition based on the first and second image data to generate decomposed basis material image data; and to derive a density information of the tissue structure of the region of interest from the decomposed basis material image data; and wherein the interface unit ( 20 ) is adapted to provide the density information to a user.