In one example, a method of examining contents of an object is disclosed comprising scanning an object by first and second radiation beams at at least first and second angles, detecting radiation at the first and second angles, and determining whether the object at least potentially comprises high atomic number material, which may be nuclear material or shielding material, based, at least in part, on the detected radiation. In one example, the detected radiation at both angles must be indicative of a region of high atomic number material by the presence of corresponding high density regions, in order for it to be concluded that high atomic number material that may be nuclear material may be present. The determination may be further based on the size of a high density region in one of the images. Systems are also disclosed.