An X-ray system (2) for acquiring an image of an object has an X-ray detector (8), which is segmented into a plurality of neighboring detector tiles. In particular, the image can be a two-dimensional projection image but also a three-dimensional volume of the object reconstructed from a tomosynthesis acquisition. An X-ray detector moving mechanism (18) is adapted for moving the X-ray detector (8) at least between a first X-ray detector position and a second X-ray detector position during operation of the X-ray system. An X-ray source (4), a collimator (22) and the X-ray detector (8) of the X-ray system (2) are adapted for acquiring a plurality of partial X-ray images through the adjacent detector tiles while irradiating the object with X-ray beams from a plurality of tomographic angles α. The processing unit is adapted for generating a two-dimension image of the object and/or for reconstructing a three-dimensional volume of the object from the acquired partial images.