Radiation therapy involves using many terms you may have never heard before. Below is a list of words you may hear during your treatment.


Active Surveillance

Also known as watchful waiting or observation, it simply means that a physician and a patient are working together to monitor the status of the disease with no treatment to be undertaken immediately. Together, the doctor and patient will decide when and if treatment is necessary.

Adjuvant Therapy

A treatment that is given in addition to the primary treatment to enhance its effectiveness and reduce the chance of the tumor recurring.


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

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Beam Films

Images created by the radiation beams themselves. They are used to verify the position of the beams to confirm that treatment is accurately delivered to the right place. Also known as port films.

Biologic Therapy

Also called immunotherapy, biologic therapy works with your immune system to fight cancer. Biologic therapy is like chemotherapy. The difference is that chemotherapy attacks the cancer directly and biologic therapy helps your immune system fight the disease better.


Pieces of metal alloy that can be used to shape the radiation beam from a linear accelerator.


Additional material placed on the patient’s skin to intentionally pull the radiation dose more superficially.


An additional dose of radiation delivered after an initial course of radiation. A boost is usually a smaller treatment in volume and is used to enhance tumor control.


Internal radiation treatment given by placing radioactive material directly into a tumor or close to it. Also called interstitial radiation therapy, intracavitary radiation therapy, intravascular radiation therapy, or seed implantation.

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Cancer develops when cells in the body begin to grow out of control. Normal cells grow, divide and die naturally. Instead of dying, cancer cells continue to grow and form new abnormal cells. Cancer cells often travel to other body parts where they grow and replace normal tissue.


A thin, flexible hollow tube used to insert temporary radioactive sources into tumors, as in breast brachytherapy or high dose rate prostate brachytherapy.

Centigray (cGy)

Abbreviated form of centigray, a unit of radiation dose equal to 0.01 gray. Equivalent to rad, the older term for radiation dose.


Treatment with drugs to destroy cancer cells. Chemotherapy is often used alone or with surgery or radiation to treat cancer.

Clinical Trials

Studies that test new treatments.


A linear accelerator attachment for electron beam treatment.


Treatment performed with an instrument that freezes and destroys abnormal tissue.

CT or CAT Scan

imaging study using X-rays and a computer to create cross-sectional pictures of the body.

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A member of the radiation oncology team skilled in translating the physician’s radiation therapy prescription into detailed instructions for the radiation therapists treating the patient. Dosimetry work involves extensive calculations and computer modeling to arrive at the optimal treatment plan for the patient. Dosimetrists are certified by the Medical Dosimetrist Certification Board.

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The use of an electric current to destroy cancerous tissue and control bleeding.


Subatomic particles with mass and negative charge used in radiation therapy to treat superficially located tumors due to their physics properties.

External Beam Radiation Therapy

Radiation therapy that uses a machine outside of the body to deliver high-energy rays directed at the cancer or tumor.

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Gray (Gy)

The amount of radiation used in radiation therapy is measured in gray (Gy), and varies depending on the type and stage of cancer being treated.

Gynecologic Oncologist

A cancer doctor who specializes in surgically removing gynecologic cancers.

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A physician who is specially trained in the diagnosis, treatment, and prevention of diseases of the blood and bone marrow as well as the immunologic, hemostatic (blood clotting) and vascular systems.

High-Dose-Rate Remote Afterloading Brachytherapy or HDR

Brachytherapy treatment employing a very small but intense radioactive source on the end of a flexible, computer-controlled cable. By inserting this radioactive source through one or more hollow applicators placed into or near a tumor, a precisely planned amount of radiation may be delivered over a short period of time.

Hodgkin’s Lymphoma

Also called Hodgkin’s disease, this is a cancer of the lymphatic system. It most often begins in the larger, most central lymph nodes of the body — those along the largest blood vessels of the neck, chest, abdomen, spine, and armpit and groin areas where the vessels return from the arms and legs. It is named for the British doctor Thomas Hodgkin who first described the disease in 1832.

Hormone Therapy

Natural hormones, such as estrogen and testosterone, help some tumors grow. To stop their growth, doctors sometimes prescribe hormone therapy to reduce the amount of hormones produced by the body in order to stop the growth of the cancer.

Hyperfractionated Radiation Therapy

A type of radiation therapy in which the radiation doses are divided into smaller amounts and patients undergo treatment more than once a day.

Hypofractionated Radiation Therapy

A type of radiation therapy in which patients undergo one or just a few treatments.

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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.
During IGRT, the images are used as a final check to ensure accurate placement of the radiation treatment.

Immobilization Device

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


Also called biologic therapy, immunotherapy works with your immune system to fight cancer.

Implant or Brachytherapy

Internal radiation therapy that involves placing radioactive sources inside or adjacent to the tumor.

Institutional Review Board

Also known as an independent ethics committee (IEC) or ethical review board (ERB), a committee that has been formally designated to approve, monitor and review biomedical and behavioral research involving humans with the aim to protect the rights and welfare of the participants in the study.

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.

Internal Radiation Therapy

A procedure in which radioactive material sealed in needles, seeds, wires, or catheters is placed directly into or near a tumor. Also called brachytherapy, implant radiation, or interstitial radiation therapy.

Interstitial Brachytherapy

A form of seed implant where radioactive sources are placed directly into the tumor (such as the prostate).

Intracavitary Brachytherapy

A type of brachytherapy where the radioactive sources are placed into a space where the tumor is located, such as the cervix or windpipe.

Intraoperative Radiation Therapy or IORT

Radiation therapy given during surgery. It is helpful when vital normal organs are too close to the tumor because it allows your radiation oncologist to avoid exposing those organs to radiation. This form of radiation therapy can be given as external beam therapy or as brachytherapy. It is currently being studied for breast cancer.

Inverted-Y Field Radiation

Treatment below the diaphragm to the abdomen, spleen and/or pelvis.

Involved Field Radiation

This is when your doctor delivers radiation only to the parts of your body known to have disease.


Also called radiation therapy or radiotherapy, it is the careful use of various forms of radiation to treat cancer and other diseases.


The single point in space where a linear accelerator’s beam is aimed regardless of the orientation of the machine.

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Abbreviation for thousand electron volts, a measure of radiation beam energy.

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Laser Surgery

A procedure where the cancer cells are killed by laser beams.


As used in radiation therapy, devices mounted on the walls and ceiling of the treatment room pointing to the treatment machine’s isocenter to allow accurate positioning of the patient from day to day.

Linear Accelerator or Linac

The most common type of machine used to deliver external radiation therapy.

Low-Dose-Rate Brachytherapy

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 seeds are permanently placed.


Breast conserving surgery that removes only the cancerous tissue. This operation is usually followed by radiation therapy.

Lymph Nodes

The lymphatic system is a network of tiny vessels extending throughout the body. They are often next to the veins and arteries but are even smaller than them. Scattered along these vessels are lymph nodes.

Lymphatic System

A network of tiny vessels extending throughout the body. They are often next to the veins and arteries but are even smaller than them. Scattered along these vessels are lymph nodes.

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Mantle Field Radiation

Radiation therapy to the parts of the body above the diaphragm to the neck, chest and/or underarm areas.


An immobilization device fitting over a patient’s head and face to allow accurate repositioning from day to day.


Mastectomy is surgical removal of the entire breast.


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


Cells located in the epidermis responsible for the production of melanin. The can suffer malignant transformation giving rise to a tumor known as malignant melanoma.

Medical Oncologist

A cancer doctor who specializes in giving drugs (called chemotherapy or targeted agents) to kill cancer cells or slow down their growth. Some medical oncologists are also hematologists, meaning they have experience treating blood disorders.


The spread of cancer from one part of the body to another. Tumors formed from cells that have spread are called “secondary tumors” and contain cells that are like those in the original (primary) tumor.

MV or MeV

Abbreviation for million electron volts, a measure of radiation beam energy .

Mohs Surgery

Also known as chemosurgery, created by a general surgeon, Dr. Frederic E. Mohs, microscopically controlled surgery that is highly effective for common types of skin cancer and squamous cell carcinoma.

Monoclonal Antibodies

Monoclonal antibodies target certain cells in the body by attaching themselves to those molecules. This causes some cancer cells to die and makes other cells more likely to be killed by radiation and chemotherapy.

MR or MRI Scan

An imaging study using a magnetic field and a computer to create cross-sectional pictures of the body.

Multileaf Collimator or MLC

Located in the head of the linear accelerator, it is used to shape the radiation beam.

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A physician trained in surgery of the nervous system and who specializes in surgery on the brain and other parts of the nervous system. Sometimes called a “brain surgeon.”

Neutron Beam Therapy

A specialized type of external beam radiation therapy using neutrons to treat tumors.

Non-Hodgkin’s Lymphoma

Also called NHL, it is a cancerous growth of the cells that make up the lymph nodes. It is eight times more common than Hodgkin’s lymphoma.

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A doctor who specializes in treating cancer. Some oncologists specialize in a particular type of cancer treatment. For example, a radiation oncologist specializes in treating cancer with radiation.

Organ Preservation

The principle that using radiation therapy and chemotherapy achieves the same local control and survival that aggressive surgery in the definitive treatment of some malignancies without the need to sacrifice the organ and the function. It is widely use in larynx, head and neck in general, esophageal, anal canal, and other organs.

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Palliative Care or Palliation

Treatment that is intended to relieve symptoms, but not cure disease.

Patient Navigator

A patient navigator is a social worker, nurse or other knowledgeable individual who can assist you in finding your way within the complex healthcare system. Patient navigators know who to call and where to go so your care can be most efficiently provided.

PET Scan

A positron emission tomography scan is an imaging study using a very small dose of a radioactive tracer attached to a sugar that is injected into the patient. Different tissues (including tumors) use the sugar at different rates, a characteristic that may be detected by the scanner to create an image of the body showing areas of tumor activity.

Photodynamic Therapy

A treatment for cancer involving three key components: a photosensitizer, light, and tissue oxygen.


Radiation therapy particle, composed exclusively of energy, with no mass or charge, that is used in radiation therapy. They can be produced in the nucleus of the atom (Gamma Radiation) or in the superficial shell (X-rays). In general, they penetrated in depth and they are used to treat deeply seated tumors

Primary Tumor

A tumor that is at the original site where it first arose.

Proton Beam Therapy

A specialized type of external beam radiation therapy using protons to treat tumors.


Radiation therapy particle, with mass and a positive charge that has a very particular penetration properties called in general “Bragg Peak”. Because of that, it can be used to treat deep tumors or tumors close to very critical structures, with minimal irradiation of those otherwise organs at risk.

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Quality Assurance (QA) Programs

The policies and procedures radiation therapy centers follow to make sure the treatment team works together to make the treatments as safe as possible. QA programs are usually created by the medical physicist. An important part of the QA program is taking precise measurements of the radiation beam and performing other safety tests on a regular basis. Patients and caregivers are encouraged to ask about the QA program at the center where they are receiving radiation treatment.

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Radiation Oncologist

A doctor who specializes in treating cancer and other diseases with radiation therapies. The radiation oncologist leads the radiation therapy treatment team.

Radiation Oncology Nurse

A member of the radiation oncology treatment team, the radiation oncology nurse works together with the radiation oncologist and radiation therapists to care for you and your family during your radiation treatments.

Radiation Physicist

A person who makes sure that the radiation machine or implant delivers the right amount of radiation to the correct site in the body. The physicist works with the radiation oncologist to choose the treatment schedule and dose that has the best chance of killing the most cancer cells.

Radiation Therapist

A health professional who gives radiation treatment.

Radiation Therapy

Also called radiotherapy or irradiation, it is the careful use of various forms of radiation to treat cancer and other diseases.


The use of radiolabeled antibodies to deliver radiation directly to a tumor.

Radiolabeled Antibodies

Monoclonal antibodies that have had a radioactive isotope attached to them in a process called radiolabeling. These antibodies are designed to attach themselves directly to diseased cells and damage them with small amounts of radiation without hurting nearby healthy cells.


A type of drug that protects normal tissues in the area being treated.


A term used to describe a tumor that does not respond well to radiation therapy.


A type of drug that can make a tumor respond better to radiation therapy.


A technique that allows your radiation oncologist to precisely focus beams of radiation to destroy certain types of tumors. It is most often called stereotactic radiotherapy.


Also called radiation therapy or irradiation, it is the careful use of various forms of radiation to treat cancer and other diseases.

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To ensure every patient is treated the best way, radiation oncologists have many checks and balances as part of treatment to ensure safety. Patients are encouraged to ask their treatment teams about the quality assurance programs where they are receiving radiation therapy.


Radioactive pellets, approximately the size of a grain of rice, used in brachytherapy.


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

Squamous Cell Carcinoma

The second most common cancer of the skin. Squamous cell carcinoma develops in the outer layer of the skin (the epithelium).


A spacer used to push tissue to a specific position relative to the radiation treatment volume.

Stereotactic Body Radiation Therapy (SBRT)

Refers to one or several stereotactic radiation treatments within the body, excluding the brain or spine.

Stereotactic Radiosurgery (SRS)

Refers to a single or several stereotactic radiation treatments of the brain or spine. SRS is delivered by a team involving a radiation oncologist and a neurosurgeon.

Stereotactic Radiotherapy

A technique that allows your radiation oncologist to precisely focus beams of radiation to destroy certain types of tumors. It is sometimes called radiosurgery.


A form of radiation where the radiation penetrates only a short distance below the surface.


A medical specialist who practices surgery.


The branch of medicine concerned with diseases and conditions which require or are amenable to operative procedures.

Surgical Oncologist

A cancer doctor who specializes in operating to cut out cancerous tumors.

Systemic Radiation Therapy

The use of radioactive isotopes that can travel throughout the body to treat certain cancers.

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Three-Dimensional Conformal Partial Breast Irradiation

A type of external beam radiation therapy where only part of the breast receives external beam radiation.

Three-Dimensional Conformal Radiotherapy (3D-CRT)

This type of external beam radiation therapy combines multiple radiation treatment fields to deliver precise doses of radiation to the affected area. Tailoring each of the radiation beams to focus on the tumor delivers a high dose of radiation to the tumor and avoids nearby healthy tissue.

Total Body Irradiation

Delivering radiation to the entire body. In the case of lymphoma, it is often done before chemotherapy and a stem cell or bone marrow transplant.

Total Nodal Irradiation

Delivering radiation to all the lymph nodes in the body

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 and organs.


An abnormal lump or mass of tissue.

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Watchful Waiting

Also known as active surveillance or observation, it is the least invasive treatment strategy that simply means that a physician and a patient are working together to actively observe the progression of the cancer or tumor.


metal filter of triangular cross-section placed within a radiation beam to intentionally feather the radiation intensity from one side of the beam to the other.

Top X


A type of high-energy radiation. In low doses, X-rays are used to diagnose diseases by making pictures of the inside of the body. In high doses, X-rays are used to treat cancer.


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