text: X-ray radiography is similar to gamma-ray radiography but instead of using a radioactive source, it uses a high-energy bremsstrahlung spectrum with energy in the 5–10 MeV range created by a linear particle accelerator (LINAC). Such X-ray systems can penetrate up to 30–40 cm of steel in vehicles moving with velocities up to 13 km/h. They provide higher penetration but also cost more to buy and operate. They are more suitable for the detection of special nuclear materials than gamma-ray systems. They also deliver about 1000 times higher dose of radiation to potential stowaways.