1. A computer readable medium embodying instructions executable by a processor to perform a method for sparse volume segmentation for 3D scan of a target, the method comprising: learning prior knowledge; providing volume data comprising the target; selecting a plurality of key contours of the volume data; building a 3D spare model of the volume data given the plurality of key contours; segmenting the volume data using the 3D sparse model; and outputting a representation of the volume data based on the segmentation using the 3D sparse model.