Medical physics Question:

Electromagnetic radiation emitted from decaying isotopes and used for external beam and brachytherapy treatments. Since it is electromagnetic radiation it is a photon and has no mass and no charge. Gamma Rays typically have similar energies to X-rays but are distinguished from these radiations by the origin of emanation. Gamma Rays are from the nucleus of the atom whereas X-Rays come from the electron shells outside of the nucleus.