1. A method for correcting artifacts caused by at least one metal object in a target region to be imaged during a reconstruction of a three-dimensional image dataset from a plurality of two-dimensional projection images of the target region recorded from mutually different projection directions with an x-ray device, the method which comprises: determining an orientation and a position of a three-dimensional model of the at least one metal object in a coordinate system of the x-ray device by way of a 2D-3D registration with a least one two-dimensional projection image; for each radiation path of the projection images running through the metal object, based on attenuation information through the metal object assigned to the model, calculating a proportion of attenuation through the metal object for the projection image data assigned to the respective radiation path and using a result of the calculation to determine modified projection images from the projection image data; and determining the three-dimensional image dataset from the modified projection images.