1. A method of segmenting a lesion from normal anatomy in a 3-dimensional image comprising the steps of: a) receiving an initial set of voxels that are contained within the lesion to be segmented; b) growing a region which includes the lesion from the initial set of voxels; c) identifying a second set of voxels on a surface of the normal anatomy; d) determining a surface containing the second set of voxels which demarks a boundary between the lesion and the normal anatomy; and e) classifying voxels which are part of the lesion.