The invention relates to a CT image generation apparatus (10) for generating an image of a head. Transformations of a first CT image of the head are determined for different measured projection groups, wherein for a measured projection group a transformation is determined such that a degree of similarity between the measured projection group and a calculated projection group is increased, wherein the calculated projection group is calculated by transforming the first CT image in accordance with the transformation to be determined and by forward projecting the transformed first CT image. A motion corrected three-dimensional second CT image is reconstructed based on the measured projections and the transformations determined for the different measured projection groups. This allows providing a high quality CT image of the head, even if a patient cannot stop moving the head in case of, for instance, stroke.
