Types of radiation therapy

Historically, the three main divisions of radiotherapy are external beam radiotherapy (EBRT or XBRT) or teletherapy, brachytherapy or sealed source radiotherapy and unsealed source radiotherapy. The differences relate to the position of the radiation source; external is outside the body, while sealed and unsealed source radiotherapy has radioactive material delivered internally. Brachytherapy sealed sources are usually extracted later, while unsealed sources may be administered by injection or ingestion. Proton therapy is a special case of external beam radiotherapy where the particles are protons. Introperative radiotherapy is a special type of radiotherapy that is delivered immediately after surgical removal of the cancer. This method has been employed in breast cancer (TARGeted Introperative radioTherapy), brain tumours and rectal cancers.
Roughly half of the 2500 worldwide radiotherapy clinics are in the US.