A computed tomography image generation apparatus for generating an image of a human head, wherein the computed tomography image generation apparatus comprises: - a projections providing unit for providing measured two-dimensional projections of the head, wherein the measured projections have been measured at different times while a radiation source, which emits radiation for traversing the head, has been moved around the head and wherein the measured projections have been generated based on the radiation after having traversed the head, - a reconstruction unit for reconstructing a three-dimensional first computed tomography image of the head based on the provided measured projections, - a transformation determination unit for determining three-dimensional transformations of the first computed tomography image of the head for different measured projection groups, wherein a measured projection group comprises one or several measured projections, wherein the transformation determination unit is adapted to determine for a certain measured projection group a transformation such that a degree of similarity between the certain measured projection group and a calculated projection group is increased, wherein the calculated projection group corresponds to the certain measured projection group and is calculated by transforming the first computed tomography image in accordance with the transformation to be determined and by forward projecting the transformed first computed tomography image, wherein the reconstruction unit is adapted to reconstruct a motion corrected three-dimensional second computed tomography image based on the measured projections and the transformations determined for the different measured projection groups, wherein the computed tomography image generation apparatus comprises an examination zone in which the human head is arrangeable, wherein the reconstruction unit is adapted to reconstruct the first computed tomography image and the second computed tomography image such that they show the examination zone and to, for generating the second computed tomography image, perform the motion correction for a first part of the examination zone and to perform the motion correction not for a second part of the examination zone, wherein the first part of the examination zone includes the human head. - a projections providing unit for providing measured two-dimensional projections of the head, wherein the measured projections have been measured at different times while a radiation source, which emits radiation for traversing the head, has been moved around the head and wherein the measured projections have been generated based on the radiation after having traversed the head, - a reconstruction unit for reconstructing a three-dimensional first computed tomography image of the head based on the provided measured projections, - a transformation determination unit for determining three-dimensional transformations of the first computed tomography image of the head for different measured projection groups, wherein a measured projection group comprises one or several measured projections, wherein the transformation determination unit is adapted to determine for a certain measured projection group a transformation such that a degree of similarity between the certain measured projection group and a calculated projection group is increased, wherein the calculated projection group corresponds to the certain measured projection group and is calculated by transforming the first computed tomography image in accordance with the transformation to be determined and by forward projecting the transformed first computed tomography image,