1. A system for segmenting image features in medical images generated with different imaging modalities, wherein the image features represent a corresponding anatomical structure, the system comprising a computer which is configured to execute a program which, when executed on the computer, causes a processor of the computer to execute a computer-implemented method, the method comprising: a) acquiring, at the processor, first modality medical image data describing a first modality medical image containing a first modality image representation of the anatomical structure; b) acquiring, at the processor, second modality medical image data describing a second modality medical image containing a second modality image representation of the anatomical structure; c) determining, by the processor and based on the first modality medical image data and the second modality medical image data, modality transformation data describing a mapping transformation between the image information in the first modality image data and the image information in the second modality image data; d) acquiring, at the processor, colour value data describing a colour value of the image elements in the first modality medical image and in the second modality medical image, wherein the colour value data comprises colour value sets of colour values for each one of the image elements in the first modality image representation and the second modality image representation, wherein each member of a set describes the colour value of one of the image elements in either the first modality image representation or the second modality image representation; e) determining, by the processor and based on the first modality medical image data, first modality segmentation data describing the result of segmenting the first modality image representation from the first modality medical image data; f) determining, by the processor and based on the first modality segmentation data and the modality transformation data and the colour value data, second modality segmentation data describing a result of segmenting the second modality image representation from the second modality medical image data, g) wherein determining the second modality segmentation data comprises correlating the colour value sets, wherein correlating the colour value sets comprises applying a cross-correlation function to the colour value sets or determining a distance between the colour values in a predetermined colour space, wherein the first modality image representation comprises a plurality of two-dimensional first modality image representations each describing an image representation of the anatomical structure, and the second modality image representation comprises a plurality of two-dimensional second modality image representations each describing an image representation of the anatomical structure, and a three-dimensional first modality image representation is determined, by the processor, from the plurality of two-dimensional first modality image representations and a three-dimensional second modality image representation is determined from the plurality of two-dimensional second modality image representations, and the modality transformation data describes a mapping transformation between the three-dimensional first modality image representation and the three-dimensional second modality image representation.