1. A method for segmenting a plurality of brain structures in a 3D magnetic resonance (MR) image, comprising: detecting a meta-structure including center positions of each of said plurality of brain structures in the 3D MR image; and individually segmenting at least one of the plurality of brain structures using marginal space learning (MSL) constrained by the detected meta-structure, wherein said step of detecting a meta-structure comprises: detecting the meta-structure using MSL to sequentially detect position, position-orientation, and a full similarity transformation of the meta-structure in the 3D MR image using a set of trained discriminative classifiers.