An interpolation of data values is performed during the acquisition of a 3D image dataset which is free of traces of a metal object imaged in the underlying 2D image datasets. A target function is defined into which data values of the 3D image dataset that are dependent on said substitute data values are incorporated following preprocessing. The substitute data values are then varied iteratively until the value of the target function satisfies a predetermined criterion. Residual artifacts that still persist following the interpolation can thus be effectively reduced.