An apparatus and a method for post processing 2D image slices (110a-c) defining a 3D image volume. The apparatus comprises a graphical user interface controller (160), a 2D segmenter (170) and a 3D segmenter (180). The apparatus allows a user to effect calculation and display of a 2D segmentation of a cross section of an object shown in a slice (110a) and calculation and display of a 3D segmentation of the object across the 3D image volume, the 3D segmentation based on the objects previously calculated 2D segmentation.
