Radiation Therapy Glossary

You may hear or read the following words in relation to radiation therapy. These definitions are meant to help you understand the terms, but are not intended as a substitute for the explanations you receive from the Therapy Team:

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Adjuvant therapy: Treatment that is used in addition to primary therapy to enhance it. Radiation therapy or chemotherapy is often used as an adjuvant to surgery.

Alopecia: Hair loss

Anesthesia: The loss of feeling or sensation as a result of drugs. General anesthesia causes temporary loss of consciousness (“puts you to sleep”). Local or regional anesthesia numbs only a certain area.

BAT (B-mode Acquisition and Targeting): A device designed to maximize the precision of external beam radiation by using ultrasound to locate and visualize tumors.

Benign: Noncancerous. A benign tumor is an abnormal but noncancerous growth that doesn’t spread to other places in the body.

Biopsy: A surgical procedure in which the tissue sample is obtained for study and identification by a pathologist.

Biopsy proven: A term describing disease that has been identified by a pathologist who examined a tissue sample.

Brachytherapy: A type of radiation therapy in which radioactive material is placed permanently or temporarily on the body, within a cancerous growth, or within a body cavity near the tumor.

Brachytherapy, High Dose Rate (HDR): A temporary type of brachytherapy in which the highly active radioactive source is used to deliver radiation into the body in a short period of time.

Brachytherapy, Low Dose Rate (LDR): Brachytherapy in which sources are left in place for the duration of treatment. This includes temporary LDR in which patients are hospitalized for several days of temporary brachytherapy. It also includes permanent LDR in which sources are permanently placed.

Cancer: A term used to describe many different diseases, all of which are characterized by perpetual abnormal cell growth and division, infiltrating locally by invasion and remotely by metastasis.

Carcinogen: A substance known to cause cancer.

Catheter: A thin, flexible tube through which fluids or other materials enter or leave the body.

Chemotherapy: Treatment of cancer with drugs given intravenously or orally.

Cobalt 60: A radioactive isotope used for gamma ray external-beam radiation therapy. This type of treatment has mainly been replaced by linear accelerators.

Conformal therapy: A type of radiation therapy in which multiple beams are shaped and angled to conform to the tumor's height, width, and depth, reducing the radiation delivered to normal tissues.

Critical structures: Normal tissues or organs near the tumor whose preservation limits the amount of radiation that can be administered.

CT scan (or CAT scan): Computed tomography scan. A series of detailed pictures of areas inside the body taken from different angles. The pictures are created by a computer linked to an x-ray machine.

Cyclotron: A charged-particle accelerator used in cancer radiation therapy for generating proton and neutron beams.

Definitive: A term used to describe radiotherapy meant to eradicate all disease.

Diagnostic radiologist: A physician who specializes in administering and interpreting such tests as X-ray studies, computerized tomography (or CAT) scans, or ultrasonography studies.

Dietitian: A specialist in proper nutrition.

Dosimetrist: Someone who calculates radiation therapy doses.

Electron beam: Radiation therapy made up of a stream of high-energy electrons. Generally this is used to treat superficial tumors.

External beam radiation therapy (or external radiation): Treatment in which the radiation source is at a distance from the body.

Fractionation: The practice of dividing a determined dose of radiation into fractions, usually administered once or twice daily.

Gamma knife: A type of stereotactic radiosurgery using multiple cobalt-60 sources.

Gamma rays: A type of electromagnetic radiation emitted from a natural radiation source, i.e. cobalt 60.

Gleason score: A system of grading prostate cancer cells describing how aggressive the cancer appears. It is used to determine the best treatment and to predict how well a person is likely to respond to treatment. The lower the Gleason score, the closer the cancer cells are to normal cells, the higher the Gleason score, the more abnormal the cancer cells.

Gray: A measure of absorbed radiation.

Hyperfractionation: A method of dosing radiation therapy in which small amounts of radiation are administered more frequently than once per day.

Image-guided radiation therapy (IGRT): A method of visualizing and localizing the tumor before each treatment. The patient can be scanned and the tumor located in 3D space immediately before treatment so that corrections can be made for patient movement and setup errors. See BAT and Tomotherapy.

Immobilization device: An apparatus that prevents movement in the treatment position.

Implant: The process by which a radiation source is placed in or near a cancer.

Intensity-modulated radiation therapy (IMRT): A highly sophisticated computer controlled method of varying the intensity and shape of the radiation beam to match the shape of the tumor while protecting surrounding normal tissue.

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

Intracavitary radiation: A radioactive source placed inside a body cavity, such as the cervix or esophagus.

Intraoperative radiation: Radiation therapy administered during a surgical operation.

Ionizing: Term used to describe electromagnetic radiation capable of producing ionization in passage through matter.

Iridium: A radioactive isotope used in brachytherapy.

Karnofsky Performance Status score: A rating from 0 to 100 indicating ability to function physically.

Linac: see linear accelerator

Linear accelerator: A machine used to produce X rays or electrons used in radiation therapy.

Malignant: describing a cancerous growth with a tendency to invade and destroy nearby tissue and spread to other parts of the body.

Medical oncologist: A physician who specializes in treating cancer with chemotherapy.

Metastasis: The spread of disease from one site in the body to one or more unconnected sites. Tumors formed from cells that have spread are called “secondary tumors” and contain cells that are like those in the original tumor. The plural form of metastasis is metastases.

Mets: see Metastasis

Multidisciplinary: Involving two or more medical specialties.

Multileaf Collimator: an attachment to the linear accelerator that shapes the radiation to conform to the tumor or treatment area.

Neutron: A neutral, uncharged subatomic particle used in cancer radiation treatment.

Oncologist: A physician who specializes in treating cancer.

Palliation (or palliative care): Therapy not meant to cure but to ease symptoms.

Portal: Treatment field.

Portal verification: Identification and matching of ideal treatment field with the actual treatment field using radiographic images or electronic portal imaging devices.

Port Film: An x-ray used to verify the position and accuracy of the treatment beam.

Proton therapy: Radiation therapy with positively charged particles accelerated into beams.

Quality of life: Subjective sense of well-being.

Radiation oncologist: A physician whose specialty is treating cancer with radiation.

Radiation physicist: A person who usually holds an advanced degree in physics who ensures that the machines used in radiation therapy administer the correct amount of radiation to patients and who, with the radiation oncologist, calculates the proper dose for individual patients.

Radiation therapist: A person specially trained and licensed to administer radiation therapy.

Radiation therapy (also called Radiotherapy): An intervention to eradicate cancer cells that employs high-energy photon, electron, neutron, and proton beams for treatment from sources outside the body and radioactive implants for treatment within the body.

Radiation therapy nurse: A registered nurse who has extensive training in oncology and radiation therapy.

Radioprotector: A drug used to protect cells from radiation.

Radiosensitizer: A drug used to sensitize cells to radiation's effects.

Radiosurgery: See Stereotactic radiation therapy.

Seeds: Radioactive pellets, approximately the size of a grain of rice, that are used in brachytherapy.

Simulation: The process of locating and marking the treatment field to be targeted in radiation therapy.

Stage: The extent of a cancer within the body, especially whether the disease has spread from the original site to other parts of the body. See Tumor Staging

Stereotactic radiation surgery: The technique used to deliver a single high-dose of radiation to a small focus of disease usually within the brain.

Surgery, reconstructive: A type of plastic surgery that restores the shape of a body area to normal.

Target volume: The area meant to receive the radiation; usually areas containing known or suspected tumors or suspected cancer cells.

Three-dimensional (3D) conformal radiation therapy: See Conformal therapy

Tomotherapy: The newest and most precise radiation therapy technology. Physicians can take images of a patient's body and treat the patient during the same session. Corrections can be made on the spot for patient movement. Radiation is delivered from all angles and modulated constantly to give low doses to certain areas of the body and higher doses to others. See IGRT.

Tumor: An abnormal mass of tissue that results from excessive cell division. Tumors perform no useful body function. They may be benign (not cancerous) or malignant (cancerous).

Tumor staging: This is an important step in the management of cancer. Typically, several tests are performed to determine 3 things. The first part is to quantify the size and extent of a primary cancer. The second is to determine whether nearby lymph nodes are involved by the cancer. The third is to check whether cancer has spread through the blood stream to other parts of the body. Using this information, people with cancer are assigned a stage. This helps to determine the best course of treatment and it also predicts the response to treatment. Each type of cancer has a specific staging system.

Treatment field: The area to be treated by radiation therapy. The area exposed to a single radiation beam.

Tumor: An abnormal lump or mass of tissue. Tumors are either benign (noncancerous) or malignant (cancerous).

Ultrasound: A test that bounces sound waves off tissues and internal organs and changes the echoes into sonograms (pictures).

X rays: High-energy electromagnetic radiation, photons.