1. A method for acquiring a 3D image dataset of an image object, comprising: acquiring a plurality of 2D image datasets of the image object at a plurality of rotational positions respectively on a trajectory by an X-ray unit, the X-ray unit comprising an X-ray radiation source and an X-ray radiation detector that can be moved in unison into the plurality of rotational positions along the trajectory about an origin of a coordinate system; acquiring a first 3D image dataset by a filtered backprojection of the 2D image datasets, wherein data value redundancies of the 2D image datasets are mutually incorporated in the first 3D image dataset; acquiring a second 3D image dataset by filtering the 2D image datasets that is antisymmetric in respect of a center of symmetry and by a subsequent backprojection of the filtered 2D image datasets, wherein the data value redundancies of the 2D image datasets are not incorporated in the second 3D image dataset; and calculating an averaged 3D image dataset by averaging the first and the second 3D image datasets, wherein the data value redundancies are eliminated in the averaged 3D image.