An apparatus for tomographic X-Ray image reconstruction, comprising: - an input unit; and - a processing unit; wherein the input unit is configured to acquire, from an input projection image sequence, first and second 2D X-Ray projection data of a region of interest of an object acquired, respectively at first and second acquisition times; wherein the input unit is configured to provide (i) first 3D rigid object data of, or approximating, a first rigid object in a region of interest of a patient, and (ii) second 3D rigid object data of, or approximating, a second rigid object in a region of interest of a patient; and wherein the processing unit is configured to generate a first registration of the first and/or second 3D rigid object data to the first 2D X-Ray projection data, to generate a second registration of the first and/or second 3D rigid object data to the second 2D X-Ray projection data, to estimate the relative motion of the second rigid object relative to the first rigid object occurring between the first and second acquisition times, and providing a relative motion vector field defining the estimated motion of the second rigid object relative to the first rigid object based on the first and second registrations, to generate corrected 2D X-Ray projection data using the relative motion vector field to correct for the motion of the second rigid object relative to the first rigid object during acquisition of the input projection image sequence, and to generate motion-compensated 3D reconstruction data of the input projection image sequence based on the corrected 2D X-Ray projection data. - an input unit; and - a processing unit; wherein the input unit is configured to acquire, from an input projection image sequence, first and second 2D X-Ray projection data of a region of interest of an object acquired, respectively at first and second acquisition times; wherein the input unit is configured to provide (i) first 3D rigid object data of, or approximating, a first rigid object in a region of interest of a patient, and (ii) second 3D rigid object data of, or approximating, a second rigid object in a region of interest of a patient; and wherein the processing unit is configured to generate a first registration of the first and/or second 3D rigid object data to the first 2D X-Ray projection data, to generate a second registration of the first and/or second 3D rigid object data to the second 2D X-Ray projection data, to estimate the relative motion of the second rigid object relative to the first rigid object occurring between the first and second acquisition times, and providing a relative motion vector field defining the estimated motion of the second rigid object relative to the first rigid object based on the first and second registrations, to generate corrected 2D X-Ray projection data using the relative motion vector field to correct for the motion of the second rigid object relative to the first rigid object during acquisition of the input projection image sequence, and to generate motion-compensated 3D reconstruction data of the input projection image sequence based on the corrected 2D X-Ray projection data. wherein the input unit is configured to acquire, from an input projection image sequence, first and second 2D X-Ray projection data of a region of interest of an object acquired, respectively at first and second acquisition times; wherein the input unit is configured to provide (i) first 3D rigid object data of, or approximating, a first rigid object in a region of interest of a patient, and (ii) second 3D rigid object data of, or approximating, a second rigid object in a region of interest of a patient; and wherein the processing unit is configured to generate a first registration of the first and/or second 3D rigid object data to the first 2D X-Ray projection data, to generate a second registration of the first and/or second 3D rigid object data to the second 2D X-Ray projection data, to estimate the relative motion of the second rigid object relative to the first rigid object occurring between the first and second acquisition times, and providing a relative motion vector field defining the estimated motion of the second rigid object relative to the first rigid object based on the first and second registrations, to generate corrected 2D X-Ray projection data using the relative motion vector field to correct for the motion of the second rigid object relative to the first rigid object during acquisition of the input projection image sequence, and to generate motion-compensated 3D reconstruction data of the input projection image sequence based on the corrected 2D X-Ray projection data.