A medical data processing method of transforming a representation of an anatomical structure of a patient in a first imaging modality into a representation of the anatomical structure in a second, other imaging modality, the method being constituted to be executed by a computer and comprising the following steps: a) acquiring first modality image data describing a first modality medical image containing the representation of the anatomical structure in the first imaging modality; b) acquiring atlas data describing a first modality atlas image describing a general structure of the anatomical structure in the first imaging modality, the atlas data containing information about the representation of the general structure in the second imaging modality; c) determining, based on the first modality image data and the atlas data, a first matching transformation between the first modality medical image and the first modality atlas image; d) determining, based on the first matching transformation and the first modality atlas image and the information about the representation of the general structure in the second imaging modality, a second modality image representation of the first modality medical image; e) acquiring second modality image data describing a second modality medical image containing the representation of the anatomical structure in the second imaging modality; f) determining, based on the second modality image representation and the second modality image data, a second matching transformation between the second modality image representation and the second modality medical image; and g) defining a structural change region in the second modality image representation, the structural change region comprising a placeholder for a data structure representing a change of the anatomical structure which is used for adapting the second matching transformation to a difference between the representations of the anatomical structure (1, 1') in the second modality representation and the second modality medical image by applying a field of shift vectors to the placeholder and correspondingly shifting and/or deforming the structures in the second modality image representation which surround the placeholder. a) acquiring first modality image data describing a first modality medical image containing the representation of the anatomical structure in the first imaging modality; b) acquiring atlas data describing a first modality atlas image describing a general structure of the anatomical structure in the first imaging modality, the atlas data containing information about the representation of the general structure in the second imaging modality; c) determining, based on the first modality image data and the atlas data, a first matching transformation between the first modality medical image and the first modality atlas image; d) determining, based on the first matching transformation and the first modality atlas image and the information about the representation of the general structure in the second imaging modality, a second modality image representation of the first modality medical image; e) acquiring second modality image data describing a second modality medical image containing the representation of the anatomical structure in the second imaging modality; f) determining, based on the second modality image representation and the second modality image data, a second matching transformation between the second modality image representation and the second modality medical image; and g) defining a structural change region in the second modality image representation, the structural change region comprising a placeholder for a data structure representing a change of the anatomical structure which is used for adapting the second matching transformation to a difference between the representations of the anatomical structure (1, 1') in the second modality representation and the second modality medical image by applying a field of shift vectors to the placeholder and correspondingly shifting and/or deforming the structures in the second modality image representation which surround the placeholder.