An improved system and method (i.e. utility) for segmentation of medical images is provided. The utility fits an estimated boundary on a structure of interest in an automated selection and fitting process. The estimated boundary may be a model boundary that is generated actual boundaries of like structures. In one arrangement, the boundaries may be selected based on the age and/or ethnicity of a patient. In further arrangements, narrow band processing is performed to estimate the actual boundary of the structure of interest.