These sources may be temporary or permanent. External beam radiation therapy is the use of gamma rays or x-rays that originate from an external source directed towards the patient. Most patients treated in radiation oncology centers receive external beam radiation therapy. Linear accelerators are used to generate high energy photon or electron beams to treat patients. These are the most common machines utilized in radiation oncology centers.
Some centers use cobalt machines that contain a strong radioactive source to produce gamma rays.
Other machines, such as orthovoltage and superficial machines, may be used in some facilities to treat skin cancers. When patients are treated with external beam radiation therapy, there are a number of planning steps taken before the first treatment is delivered. After a consultation with the radiation oncologist, special radiologic studies may be ordered to help plan the radiation treatments. These may include masks, casts, molds, and special mouth pieces depending on the area of the body that requires treatment. Next, a simulation is performed.