ABSTRACT
Treatment of cancer with radiation from various sources continues to be common, with approximately 50% of all cancer patients receiving radiation therapy. The routinely used sources of radiation include linear accelerators, 60Co units, medium-energy X-ray machines, and sealed and unsealed radioactive materials. Most patients are irradiated externally in a procedure known as Teletherapy. Linear accelerators are commercially available which produce beams of photons and electrons in the energy range of 4 to 25 MeV for teletherapy applications. X-ray machines which operate in the range of 100 to 300 kV are still in use but are being replaced with electron beams from accelerators for treatment of superficially located tumors. Sealed radioactive sources in the form of tubes, needles, wires, and seeds are used in intracavitary or interstitial applications often in conjunction with teletherapy in procedures which are known as Brachytherapy. 131I and 32P are administered to patients for the treatment of a small number of diseases.
