Glossary of Radiation Oncology Terms

University of Wisconsin Carbone Cancer Center provides this glossary of radiation oncology terms.


Applicator: A device used to hold a radioactive source in place during brachytherapy.

Beam Films: Another term for port films, beam films are pictures of the position of the radiation beams used to treat cancer. They are used to verify the position of the beams and confirm that treatment is delivered to the right place.

Blocks: Pieces of metal alloy that can be used to shape the radiation beam. Also called cerrobend.

Boost: An additional dose of radiation that is given after an initial course of radiation to enhance tumor control.

Brachytherapy or Implant: Internal radiation therapy that involves placing radioactive sources inside or next to a tumor. More about Brachytherapy

Cancer: A group of diseases in which abnormal cells divide uncontrollably, forming a tumor or mass.

Clinical Trials: Studies that test new cancer therapies. More about Clinical Trials

Image-guided Radiation Therapy or IGRT: A radiation treatment guided by imaging equipment, such as CT, ultrasound, or x-rays, taken in the treatment room just before radiation is given. More about IGRT

Immobilization Device: A device that is used to help a patient remain in the same position during every treatment.

Intensity-modulated Radiation Therapy or IMRT: IMRT is a specialized form of external beam therapy that can help improve how the radiation is shaped to fit your tumor. More about IMRT

Linear Accelerator or Linac: The most common type of machine used to deliver external radiation therapy.

Metastases: Cancer that has spread from one part f the body to another, such as from the breast to the lymph nodes or bones.

Multileaf Collimator or MLC: A part of a linear accelerator that is used to shape the radiation beam.

Palliative Care or Palliation: Treatment that is intended to relieve symptoms, but not cure disease.

Radiation Oncologist: A doctor who specializes in treatment cancer and other diseases with radiation therapy.

Radiation Therapy or Radiotherapy: The use of radiation to treat cancer and other diseases.

Simulation: The process of planning radiation therapy to allow the radiation to be delivered to the intended location.

Tomotherapy: A type of machine has the ability to image a patient and deliver radiation therapy treatments. More about Tomotherapy

Treatment Plan: A radiation oncologist’s prescription describing how a patient should be treated with radiation therapy. The radiation oncology team uses special software to maximize radiation to the tumor while sparing healthy tissue.