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Radiation  Therapy  -  External  Beam

Approximately 50% of all cancer patients will receive some type of radiation treatment. Radiation therapy is
external radiation treatment in which doctors use focused beams of radiation to treat cancerous tumors. It is
just one of the many different methods of radiation treatment administered in hospitals. There are different
types of radiation therapy: external beam therapy, three-dimensional conformal radiation therapy, and
stereotactic radiosurgery.

    •  External Beam Therapy delivers a single beam of high-energy x-rays to the location of the patient's
       tumor. The beam is generated outside the patient, by a machine called a linear accelerator, and is
       targeted at the tumor site. These treatments are usually performed in multiple sessions over the course
       of several weeks.
    •  Intensity-Modulated Radiation Therapy uses a computer simulation to produce an accurate image of
       the tumor and surrounding organs so that multiple radiation beams can be shaped exactly to the
       contour of the treatment area. Because the radiation beams are precisely focused, nearby healthy
       tissue is spared.
    •  Stereotactic Radiosurgery is not, as the name suggests, a form of surgery. It is usually a one-day
       treatment of a single high-dose—or sometimes smaller, multiple doses—of radiation beams that
       converge on the specific area of the brain where the tumor or other abnormality resides. Using a
       helmet-like device that keeps the head completely still and three-dimensional computer-aided
       planning software, stereotactic radiosurgery minimizes the amount of radiation to healthy
       brain tissue.
These methods are painless, treat various types of cancer, and  often work in conjunction with other forms of
treatment (e.g., chemotherapy or surgery). The linear accelerators used in these treatments emit high-energy
x-rays,a form of electromagnetic ionizing radiation. Ionizing radiation is high-energy radiation capable of
stripping electrons from atoms. The free electrons have the ability to damage living cells, such as in tumors.
This is how radiation therapy stops cancer cells from dividing  and growing, thus slowing tumor growth. In
many cases, radiation therapy is capable of killing cancer cells, thus shrinking or eliminating tumors.

The machine sits in a room with lead and concrete walls so that the high-energy x-rays do not escape. The
radiation therapist must turn on the accelerator from outside the treatment room. One of the benefits of
accelerators is that, unlike radioactive sources, they only produce radiation when they are operated.


Who is  protecting  you

The States
State radiation programs, in cooperation with the Food and Drug Administration, regulate, register, and
inspect x-ray equipment used in medical, dental, and veterinary work.

U.S. Food  and Drug Administration (FDA)
While the states regulate use of x-ray equipment, FDA's  Center for Devices and Radiological Health
regulates the  manufacturing of radiation-emitting electronic products.
 United States Environmental Protection Agency
Office of Radiation and Indoor Air (6608J)  |   EPA 402-F-06-034
April 2006
                                                                www.epa.gov/radtown/radiation-therapy.html

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 RadTown  USA
National Institute of Standards and Technology (NIST)

The mission of NIST is to develop and promote measurement, standards, and technology to enhance
productivity, facilitate trade, and improve the quality of life. Although anon-regulatory federal agency, NIST
makes x-ray machines safer for patients and workers by updating the technology and measurement standards
upon which x-ray machines are based.


What you can do to protect yourself

Only trained and qualified persons should operate the accelerator. You should follow any instructions given
by your doctor, nurse, or the radiation therapist. You should tell your doctor if you are  pregnant, might be
pregnant or are nursing. Finally, if you have any concerns or questions before undergoing medical testing or
treatment involving radiation, don't hesitate to ask your doctor or the radiation therapist.


Resources

You can explore this radiation  source further through the resources at the following URL:
http://www.epa.gov/radtown/radiation-therapy.htmltfresources

We provide these resources on-line rather than here so we can keep the links up-to-date.
 United States Environmental Protection Agency
Office of Radiation and Indoor Air (6608J)  |   EPA 402-F-06-034
April 2006
                                                                 www.epa.gov/radtown/radiation-therapy.html

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