The invention relates to a data processing method of determining a positional transformation (T, M) for correcting the registration of an anatomical body part with a medical imaging apparatus, the method being executed by a computer and comprising the following steps: a) acquiring initial body part position data comprising initial body part position information describing an initial relative position (1) between the medical imaging apparatus and the anatomical body part; b) acquiring, from the medical imaging apparatus, body part medical image data comprising body part medical image information describing an image of the anatomical body part; c) acquiring, based on the body part medical imaging data, actual body part position data comprising actual body part position information describing an actual relative position (2, 4) between the anatomical body part and the medical imaging apparatus; d) determining, based on the actual body part position data and the initial body part position data, body part position transformation data comprising body part position transformation information describing a transformation (T, M) between the initial relative position (1) between the anatomical body part and the medical imaging apparatus, and the actual relative position (2, 4) between the anatomical body part and the medical imaging apparatus.