A computer-implemented method for operating an X-
ray device for acquiring projection images of an acquisition area, from which a three-dimensional image dataset of the acquisition area is reconstructed. The X-
ray device has an acquisition arrangement with an X-
ray generator and an X-ray
detector for receiving X-
ray radiation of an X-ray field which has a central beam and which is transmitted by the X-ray generator. For acquiring projection images of different projection directions, the acquisition arrangement is moved rotationally to cover a projection
angular range encompassing at least 360° about the acquisition area. An opacification device is used that includes an opacification pattern that includes a section opacifying the X-
ray radiation with at least two opacifying areas and a section permeable to the X-
ray radiation with at least two permeable areas separated by an opacifying area. The opacification device is arranged in the X-ray field between the X-ray generator and the acquisition area such that each
voxel to be reconstructed in the acquisition area, and which is opacified in a partial area of the rotation, is scanned by non-opacified X-ray
radiation in another partial area of the rotation, that includes at least substantially the same number of acquisition geometries and / or encompasses a 180° angular section with respect to the projection of the
projection direction into the plane of rotation.