Understanding Radiation Therapy

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Radiation therapy glossary

These are words that you may hear your health care team use.

Accelerated radiation: a radiation schedule in which the total dose is given over a shorter period of time. Compare to hyperfractionated radiation.

Adjuvant therapy (ad-juh-vunt): a treatment used in addition to the main (primary) treatment. Radiation therapy often is used as an adjuvant to surgery.

Alopecia (al-o-pee-shuh): hair loss, including face and body hair

Anesthesia (an-es-THEE-zhuh): loss of feeling, sensation, or consciousness caused by certain drugs or gases. Also used to describe the drug or gas used to cause this.

Anti-emetic (an-tee-ih-MEH-tik or an-tie-ih-MEH-tik): a drug to prevent or treat nausea or vomiting

Applicator (AP-lick-ate-ur): a device used to put an implant or medicine into the body

Benign tumor (be-nine too-mer): a tumor (lump or mass) that is not cancer

Biologic therapy (by-o-LA-jick): treatment that uses the immune system to fight infection and disease. Also called immunotherapy or immune therapy.

Biopsy (by-op-see): the removal of a piece of tissue that is looked at under a microscope to see if it contains cancer or other abnormal cells

Brachytherapy (brake-ee-THER-uh-pee): internal radiation treatment done by putting radioactive material right into the tumor or close to it. Also called internal radiation therapy.

Cancer: a general term for more than 100 diseases that have uncontrolled, abnormal growth of cells that can spread into and destroy healthy tissues

Catheter (cath-ih-tur): a thin, flexible tube through which fluids or other materials can be put in or taken out of the body

Centigray (cGy) (sent-uh-gray): the preferred measurement of the amount of radiation dose absorbed by the body (1 cGy = 1 rad)

Chemotherapy (key-mo-THER-uh-pee): the use of certain types of drugs to treat cancer

Conformal radiation therapy (con-for-mul): a newer type of radiation treatment that uses a special computer to help shape the beams of radiation to match the shape of the tumor and delivers the beams from different directions rather than from one angle. This reduces the amount of radiation reaching nearby healthy tissues.

Dietitian or registered dietitian (die-uh-TISH-un): a health professional who plans well-balanced diet programs, including special diets to meet the needs of people with various medical conditions

Dosimetrist (doe-sim-uh-trist): a person who plans and calculates the proper radiation dose for each patient’s cancer treatment

Electron beam (ee-leck-tron): a stream of high-energy particles called electrons used to treat some skin cancers

External radiation: radiation therapy that uses a machine located outside of the body to aim high-energy rays at cancer cells

Fractionated radiosurgery (frack-shun-ate-ed): see stereotactic radiosurgery

Fractionation (frack-shun-A-shun): dividing the total dose of radiation into smaller doses (usually given over weeks) in order to reduce damage to healthy tissues

Fractions: the smaller, divided doses of radiation that are given each day

Gamma rays: high-energy rays that come from a radioactive element such as cobalt-60 or radium

Helical tomotherapy (he-lick-ul toe-moh-THER-uh-pee): a newer form of intensity modulated radiation therapy (IMRT) in which the radiation is directed from a donut-shaped machine that spirals around the body

High-dose-rate (HDR) brachytherapy: a type of internal radiation in which the radioactive source is in place only for a short time and then removed. This may be repeated several times over a few days to weeks. See brachytherapy.

Hyperfractionated radiation (hi-per-FRACK-shun-ate-ed): a radiation schedule in which the radiation is given in smaller doses and more than once a day, but the overall length of treatment is the same. Compare to accelerated radiation.

Immune therapy: treatment that uses the immune system to fight infection and disease. Also called biologic therapy or immunotherapy.

Implant, radioactive: a small source or container of radioactive material placed in the body, either in or near a cancer. See brachytherapy.

Intensity modulated radiation therapy or IMRT (in-ten-si-tee MOD-you-late-ed): an advanced method of conformal radiation therapy in which the beams are aimed from many directions and the intensity (strength) of the beams is controlled by computers. This allows more radiation to treat the tumor while reducing the radiation to healthy tissues. See conformal radiation therapy.

Internal radiation: a type of therapy in which a radioactive substance is put into or close to the area needing treatment. Also called brachytherapy.

Interstitial radiation (in-ter-STISH-uhl): a type of internal radiation in which a radioactive source (implant) is put right into the tissue (not in a body cavity). Compare to intracavitary radiation.

Intracavitary radiation (in-truh-KAV-uh-tair-ee): a type of internal radiation in which a radioactive source (implant) is placed in a body cavity, such as the vagina or rectum, as opposed to right into a tumor. Compare to interstitial radiation.

Intraoperative radiation (in-truh-OP-er-uh-tiv): a type of external radiation therapy used to deliver a large dose of radiation to the tumor during surgery

Linear accelerator (lin-ee-uhr ak-SELL-er-a-ter): a machine that creates high-energy radiation to treat cancers using electricity to form a beam of fast-moving subatomic particles called photons (foe-tahns). Also called a linac.

Malignant (muh-lig-nunt): cancerous; a malignant tumor or mass of cells is called cancer

Medical oncologist (med-ih-kull on-kahl-uh-jist): a doctor who is specially trained in the diagnosis and treatment of cancer and who specializes in the use of chemotherapy and other drugs to treat cancer

Medical social worker also called clinical social worker: a mental health professional with a master’s degree in social work (MSW). A social worker can help people manage medical, psychological, social, and educational needs.

Metastasis (meh-tas-tuh-sis): the spread of cancer cells to distant areas of the body by way of the lymph system or bloodstream. Also used to describe the area to which cancer has spread. The plural is metastases (meh-tas-tuh-sees).

Monoclonal antibody (ma-nuh-KLO-nuhl AN-tih-bah-dee): man-made antibodies that are designed to lock onto certain antigens (substances that can be recognized by the immune system). Monoclonal antibodies can be attached to chemotherapy drugs or radioactive substances and deliver these treatments directly to the cancer cells, killing them with little risk of harming healthy tissue.

Oncologist (on-kahl-uh-jist): a doctor who specializes in caring for people with cancer

Oncology (on-kahl-uh-jee): the branch of medicine devoted to the diagnosis and treatment of cancer

Palliative care (pal-ee-uh-tiv): treatment intended to relieve symptoms caused by cancer, rather than cure cancer. Palliative care should be part of all phases of cancer treatment and can help people live more comfortably.

Physical therapist: a health professional who helps people use exercises and other methods to restore or maintain body strength, mobility, and function

Platelets (plate-lets): special blood cell fragments that help stop bleeding

Port (also radiation port or treatment field): the area of the body through which external beam radiation is directed to reach a tumor

Prosthesis (pros-thee-sis): an artificial replacement for a part of the body

Proton beam therapy (pro-tahn): a form of external radiation that uses proton beams to kill cancer cells. Protons are parts of atoms that cause little damage to tissues they pass through but are very good at killing cells at the end of their path.

Rad: short for “radiation absorbed dose;” an older term of measurement of the amount of radiation absorbed by the body (1 rad = 1 cGy). See centigray.

Radiation: in cancer treatment, energy carried by waves or a stream of particles. Types of radiation used to treat cancer include x-rays and gamma rays; electrons, protons, neutrons, and alpha and beta particles. Radioactive substances include forms of cobalt, radium, iridium, cesium, iodine, strontium, samarium, phosphorus, and palladium.

Radiation oncologist: a doctor who specializes in using radiation to treat cancer

Radiation physicist (fizz-uh-sist): a person trained to ensure that the radiation machine delivers the right amount of radiation to the treatment area. This person works with the radiation oncologist and dosimetrist to design, plan, and calculate the proper dose for radiation treatment. See dosimetrist.

Radiation therapist: a person with special training to use the equipment that delivers radiation

Radiation therapy or radiation treatment: the use of high-energy rays or subatomic particles that travel into the body to kill cancer cells

Radiation therapy nurse: a registered nurse who has special training in cancer and radiation therapy

Radiologist: a doctor with special training in reading and interpreting x-rays and scans and doing special x-ray procedures

Radiopharmaceuticals (ray-dee-o-farm-uh-SUIT-ih-kulls): radioactive medicines that are taken by mouth or injected into the body. They collect in the area of the tumor and help stop its growth.

Radio-resistance: the ability of cells to not be affected by radiation

Radiosensitivity (ray-dee-oh-SENS-ih-tiv-it-tee): how susceptible a cell is to radiation, or how easy it is for radiation to kill the cell. Cells that divide frequently are especially radiosensitive and are more affected by radiation.

Simulation: a process involving special imaging tests, which are used to plan radiation treatment so that the area to be treated is precisely located and marked

Stereotactic radiosurgery (steer-e-o-TACK-tick ray-dee-o-SUR-jer-ee): a type of treatment that uses thin beams of radiation given from many angles to give a large dose of radiation to a small tumor area, usually in one session. Though it’s called surgery, no knife or scalpel is used. The treatment may be useful for tumors in places where surgery can’t be done, for example, in parts of the brain or spinal cord, or when the patient’s condition does not permit surgery.

Systemic radiation: the use of radioactive materials like iodine 131 or strontium 89 to kill cancer cells. The materials may be taken by mouth or injected into the body. See radiopharmaceuticals.

Teletherapy (tell-uh-THER-uh-pee): treatment in which the radiation source is at a distance from the body (external radiation)

Treatment field (or port): the area of the body through which external beam radiation is directed to reach a tumor

Tumor: an abnormal lump or mass of tissue. Tumors are either benign (not cancer) or malignant (cancer).

Unsealed radiation: internal radiation therapy that is swallowed or given by injecting a radioactive substance into the bloodstream or a body cavity. This substance is not sealed in a container or implant.

White blood cells: the blood cells that help defend the body against infection

X-ray: a form of radiation that can be used either at low levels to make a picture of the inside of the body or at high levels to kill cancer cells


Last Medical Review: 05/02/2014
Last Revised: 05/02/2014