 Treatments of cancer by x-ray today generally follows Coutard's fractionated process, while radiated rods are used in brachytherapy.The three main divisions of radiation therapy are external beam radiation therapy or teletherapy, brachytherapy or sealed source radiation therapy, and systemic radioisotope therapy or unsealed source radiotherapy.The differences relate to the position of the radiation source; external is outside the body, brachytherapy uses sealed radioactive sources placed precisely in the area under treatment, and systemic radioisotopes are given by infusion or oral ingestion.