External Beam Radiation
External beam radiation (EBRT) is the most common type of radiation. With EBRT, the patient is on a treatment table for 5-15 minutes and the radiation beams are directed to the tumors from outside of the body. Various pads and support devices are used to assist the patient with comfort and minimize the motion of the body. The sensation of claustrophobia (anxiety of enclosed spaces) is not a problem with external beam radiation since the radiation equipment is a comfortable distance away from the patient.
Radiation may consist of one beam, but more commonly will consist of two or more beams. Radiation beams are a type of invisible energy which have no symptoms or sensation as they enter the body (light is a form of visible energy). Radiation is given in sufficient doses to damage DNA in the chromosomes of tumor cells. This damage prevents the tumor cell from dividing and becoming two cells. The radiation oncologist is trained in selecting doses of radiation which kill tumor cells without killing significant numbers normal cells. This is due in part to tumor cells having greater sensitivity to radiation normal cells (therapeutic window).