1. A method of classifying objects using volumetric multi-energy CT images, wherein a CT image and a Z (atomic number) image are provided, wherein a potential threat object is also provided, comprising: a. Dividing the potential threat object into different geometrical portions; b. Computing the local distribution features for each portion of the potential threat object; and c. Classifying the potential threat object as a threat or a non-threat using the local distribution features.