The present invention relates to an apparatus for characterization of a feature in a body part. It is describe to provide (210) tomosynthesis medical data comprising a plurality of images of the body part, wherein the plurality of images comprise image data associated with a plurality of rays of radiation that have passed through the body part, wherein the image data comprises spectral data associated with at least two photon energy levels of the plurality of rays of radiation, wherein the medical data comprises data of the feature. A delineated boundary of the feature is determined (220). At least one material composition of the body part inside the delineated boundary is determined (240) comprising a function of the spectral data inside the delineated boundary. The feature is characterised (250) as a function of the at least one material composition inside the delineated boundary of the feature. Data representative of the feature is output (260).