Radiation Treatment is either given externally or internally, and it involves use of either beams or radioisotopes to deliver gamma rays [high energy Xrays], or protons, or neutrons, or electrons, or alpha particles to the tumor. The idea is to get a high dose of radiation to the tumor while the surrounding normal tissue is protected from radiation damage.

External Radiation involves beams of either high-energy rays, or neutrons, or electrons or protons.  External radiation therapy does not cause your body to become radioactive.