This machine employs Cobalt 60 as a source of gamma rays to treat tumors.The source is a small cylinder filled with cobalt pellets. It is surrounded by a solid spherical shield of lead 22 inches in diameter. The ray issues through a passage in the lead shield; and a collimator, below the head, controls the ray’s shape to match the tumor . The head, embodying the lead sphere, weighs as much as a medium sized automobile, and the entire machine weighs about seven tons. The structure consist of cast stainless steel, including the lower extension which is a solid eight inches thick. This serves as a combined counterweight for the head and shield for the gamma ray after it passes through the patient. -Lawrie McIntosh Click here to see the next generation, Theratron 780