1. A system for segmenting an object in image data using model-based image segmentation, the system comprising a feature unit for identifying features in the image data for computing an external energy of a mesh on the basis of a current position of the mesh, wherein the feature unit further comprises: a candidate feature unit for selecting a plurality of candidate features in the image data, for identifying a feature to be included in the features identified in the image data; a position unit for determining a position of each candidate feature of the plurality of the candidate features relative to a region of the image data, wherein each of the candidate features is within the region; a feature value unit for computing a feature value of each of the candidate features; a feature function unit for computing a strength of each of the candidate features, wherein the strength of each of the candidate features depends on the feature value of the corresponding candidate feature and the ratio of the strength and the feature value of each of the candidate features depends on the position of the corresponding candidate feature relative to the region; and an evaluation unit for evaluating each of the candidate features of the plurality of candidate features and for identifying the feature to be included from among the plurality of candidate features based on this evaluation.