Searching for explosives in suitcases
On the left (A), three gamma rays radiographies of a suitcase : Top, normal radiography where the darker parts indicate denser areas; in the middle "resonance" radiography, where darker areas represent higher density of nitrogen. Bottom, the combination of normal and resonant radiographiies reveals a stick of semtex explosive. On the right (B), the radiographies of a second suitcase This time the explosive is hidden in a double-bottom lid.