Abstract: A method of creating a segmentation of a volume of interest in an object data set is described, which object data set is formatted into object data slices, in which at least two object data slices each contain a contour line defining the portion of the volume of interest present in that object data slice as a region of interest. The method comprises the steps of calculating at least one surface which cuts through each of the at least two regions of interest, defining two curves on each surface which intersect with the contour lines, arranging for those curves to define the portion of the volume of interest present in the surface, calculating on each of the remaining object data slices a contour line which includes those points on the curves which intersect with that object data slice. A computer program and work station are also described.