The goal of this challenge is to identify the best methods of segmenting brain structures that serve as barriers to the spread of brain cancers and structures to be spared from irradiation, for use in computer assisted target definition for glioma and radiotherapy plan optimization. The segmentation of brain structures is a challenging task as different structures can be visually appreciated more or less favorably on different imaging modalities. Furthermore, as multi-modality images are usually acquired at different time points, they could present subtle anatomical differences even for brain imaging. This presents a unique technological challenge as information from multi-modality imaging is used to define the clinical target volume and the healthy organs for each individual patient's disease.