1. A method for the interactive segmentation of a structure contained in an object from a three-dimensional image of the object, which method involves a continuous visualization of the instantaneous segmentation status in a segmentation image and includes an expansion mode and a contraction mode, the following steps being carried out in the expansion mode a) determining the similarity between the neighboring voxel of a defined voxel and the structure, b) storing the order in which the similarity of the voxels belonging to the structure is determined, c) repeating the steps a) and b) for voxels of the structure which have not yet been processed or have been newly determined, while in the contraction mode the voxels are removed, on the basis of the instantaneous segmentation tatus, from the segmented structure in an order which is the reverse of that in which they have been determined as belonging to the structure in the expansion mode.