A tomography apparatus that generates images of an object includes a radiation source emitting a radiation beam, wherein the radiation beam rotates around the object and penetrates the object; a radiation detector rotating around the object opposite the radiation source so that the radiation detector detects the radiation beam after penetration of the object; a radiation mask surrounding the object that masks the radiation beam, wherein the radiation mask is arranged in a path of the radiation beam between the radiation source and the radiation detector and the radiation beam passes the radiation mask only once between the radiation source and the radiation detector.