Glossary of Radiation Terms
Adjuvant therapy:
Radiation therapy, chemotherapy, or both, given as additional treatment for a cancer that has been or will be removed surgically.
Block:
A thick piece of metal used to shield certain areas of the body from the X-ray or electron beam. Blocks are customized for each patient, but not all treatments require blocks.
Boost:
An additional dose of radiation that is given after an initial course of radiation to enhance tumor control.
Brachytherapy:
A minimally invasive treatment in which tiny radioactive sources are implanted through hollow needles or catheters in to the area needing treatment. This alternative to surgery concentrates radiation on the tumor site while minimizing exposure to surrounding healthy tissues. Brachytherapy has been proven successful in treating a variety of cancers, particularly prostate cancer and gynecological malignancies.
Cancer:
A general term for more than 200 diseases characterized by abnormal and uncontrolled cell growth. The resulting mass, or tumor, can invade and destroy surrounding normal tissues.
Chemotherapy:
Treatment with anticancer drugs. Chemotherapy is usually given through the vein, but some drugs are given by mouth. Concomitant chemotherapy is chemotherapy given at the same time as radiation. Sequential chemotherapy is chemotherapy given before or after radiation therapy.
CT scanner:
A computerized diagnostic X-ray machine that gives images of the inside of the body. Also known as a “CAT ” scan, CT scans can be used during planning or simulation.
Cyberknife™:
A specialized linear accelerator mounted on a robotic arm for stereotactic radiosurgery (SRS). The Cyberknife can deliver radiation from almost any direction, track the target position during treatment, and make adjustments based on any patient or target movement.
Dosimetrist:
A specially trained technologist who helps design external beam radiation treatments. The dosimetrist works closely with the radiation physicist.
Electron beam:
A type of penetrating radiation generated by a linear accelerator, where electrons are accelerated to high energies. Electron beams can kill cancer cells.
Electronic portal imaging device (EPID):
A digital imaging device used to monitor and manage target positioning during the course of treatment (port films).
External beam radiation:
Radiation therapy using a machine that focuses radiation on a part of the body.
Fiducial markers:
Also called “marker seeds” or “gold seeds,” these are small markers implanted near your tumor to help with tracking the target in your body. These markers are usually placed during a separate outpatient appointment.
Field:
The projection of the radiation beam from the machine onto the patient. The shape and size of the field is based on the target and created by the multileaf collimators.
Fluoride therapy:
Daily self-application of prescription-strength fluoride. This helps prevent excessive tooth decay in teeth that are in the radiation field.
High-dose rate (HDR) brachytherapy:
A type of internal radiation treatment in which the implanted radioactive source is removed between treatments. Because of the high dose rate, treatment time is relatively short. This procedure might require hospitalization.
Hormone:
One of many naturally occurring chemical substances in the body that regulate body systems. For example, insulin is a hormone that regulates the sugar level in the body.
Hormone therapy:
Also known as endocrine therapy, hormone therapy is the use of hormone-like drugs to control certain cancers. Prostate and breast cancer are examples of cancers that may be treated with hormone therapy.
Image-guided radiation therapy (IGRT):
IGRT is the use of X-ray, CT scan, or ultrasound pictures, taken just prior to or during treatment, to guide treatment delivery. The tumor can be precisely located in 3-D space immediately before treatment. The ability to correct for movement and any errors during setup means smaller margins can be used, sparing healthy tissue and escalating the tumor dose.
Immobilization device:
Customized equipment, such as masks and form-fitting bean bags, made at the time of planning and used with each treatment in order to increase accuracy and recapture positioning.
Implant:
A small container of radioactive material that is placed inside a tumor.
Intensity-modulated radiation therapy (IMRT):
IMRT is a recent technology that allows for even more precise radiation delivery using linear accelerators. With IMRT , the intensity of the radiation beam can be varied, allowing precise 3-D targeting of tumors. This technology is particularly useful in treating complex tumors that have spread close to sensitive parts, such as the spinal cord and salivary glands.
Internal radiation (interstitial and intracavitary radiation):
A type of radiation therapy, also called brachytherapy, in which a radioactive substance is implanted in the area of the body needing treatment.
Linear accelerator (LINAC):
A machine that creates and uses high-energy X-rays or electron beams to treat cancer.
Mask:
A custom-made plastic mold of the patient’s head used to keep the head in the proper position during treatment of brain, head, and neck tumors.
Medical oncologist:
A physician who has trained in internal medicine and received specialized training in using chemotherapy and other medications to treat cancer.
Multileaf collimator (MLC):
A device that helps shape the X-ray beam produced by the linear accelerator (LINAC). It consists of many computer-controlled metal leaves that move back and forth to focus the beam and better avoid normal tissue.
On-board imager (OBI):
A high resolution, low-dose digital imaging device mounted on the linear accelerator that is used to improve tumor targeting.
Oncologist:
A physician who specializes in diagnosing and treating cancers.
Port film:
An X-ray picture taken at the start of and during treatment by the electronic portal imaging device (EPID) to make sure that the treatment beam is aimed correctly.
Radioactive:
Giving off radiation.
Radiation oncologist:
A physician who has received specialized training in using radiation to treat cancer.
Radiation oncology nurse:
A nurse who has received specialized training in the care of cancer patients receiving radiation therapy.
Radiation oncology social worker:
A social worker who has received special training to provide support and counseling to people with cancer.
Radiation physicist:
A person trained in the physics of radiation therapy. Radiation physicists prepare treatment plans, run treatment computers, and make sure that the machines are functioning properly.
Radiation therapist:
A specially trained therapist who administers external radiation treatment using the individualized plans prepared by the radiation oncologist.
Radiation therapy:
The use of highenergy penetrating rays to treat disease. Radiation can be produced by machines, such as the linear accelerator (LINAC), or emitted by radioactive sources, as used in brachytherapy.
Radiosurgery:
See stereotactic radiation therapy.
RapidArc™:
An intensity-modulated radiotherapy (IMRT ) technique allowing for complete daily treatment in a single rotation of the linear accelerator (LINAC) around the patient.
Simulation:
Also known as planning. Simulation is the process of designing treatment fields and calculating the details of treatment.
Stereotactic Radiosurgery (SRS):
Sometimes referred to as radiosurgery or stereotactic radiation therapy. SRS is a focused, high-dose form of external beam radiation that is used to treat highly selected types of cancer and some benign diseases. The term “radiosurgery” is used to describe treatment with very high radiation doses, typically given in one to five treatments. Stereotactic refers to the ability to localize the target with sub-millimeter accuracy during treatment.
Tattoos:
Tiny, permanent ink dots marked on your skin in or near the treatment area during the planning phase. These marks are used each day before treatment to align your body in the accurate position.
Three-dimensional conformal radiation therapy (3D-CRT):
Radiation therapy treatment that uses a higher dose of radiation that is shaped to conform to a 3-D target. Total body irradiation Irradiation applied to the whole body, typically to prepare for a bone marrow transplant. Trilogy™ A model of a linear accelerator capable of 3D-CRT, IMRT, IGRT, and stereotactic radiosurgery (SRS) treatments.
X-rays:
A type of penetrating radiation generated by a machine. Depending on the machine and the energy of the X-ray, it can be used for imaging (chest X-ray) or for killing cancer cells.
