The systems and methods described herein automatically detect, highlight and identify high-Z materials in volume concentrations of approximately 100 cm.sup.3 or greater utilizing single and/or dual energy sources with x-ray and neutron detectors. The methods and systems described herein are applied to the imaging of containerized cargo and cargo vehicles. Pursuant to the described systems and methods, radiation powers are orders of magnitude lower than those used in the conventional systems. By reducing the radiation power by a factor of, for example, 100 or more, the shielding requirements for the system are greatly reduced, alignment requirements can be significantly relaxed and system components can be lighter weight and more modular. Consequently, system costs are reduced.