1. A method for segmenting an image, comprising the steps of: performing an initial segmentation of the image to produce a previous segmented region; segmenting iteratively the image using a spatial random walk based on a shape prior of the previous segmented region to produce a next segmented region, wherein the spatial random walk is minimizing an energy function E with the shape prior according to E=E rw +vE sp , wherein E rw is an energy of a random walk segmentation, E sp is an energy of the prior shape, and v is a weight parameter controlling an impact of the shape prior into the spatial random walk; comparing the next segmented region with the previous segmented region; repeating the segmenting and the comparing until the previous and next segmented regions converge; and selecting the next segmented region as a final segmented region.