Radiation Therapy - External Beam
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Printer Friendly VersionRadiation Therapy (PDF)
This page provides information on the medical treatments that involve focused beams of radiation to treat cancerous tumors.
On this page:
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 stereo tactic radio surgery.
- 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
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.
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 a non-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.
|How Radiation Works
April 5, 2012. Breastcancer.org
On this page, you can learn more about how external radiation treatment works, specifically in treating breast cancer.
|External Beam Radiation Therapy
April 5, 2012. U.S. National Institutes of Health, National Cancer Institute
This page gives information on the steps leading up to external radiation therapy. It also discusses what you should expect during the treatment.
|External Beam Therapy
April 5, 2012. American College of Radiology and Radiological Society of North America
On this site, you can read more about external beam therapy.
|Breast Health: Radiation Therapy for Breast Cancer Treatment
April 5, 2012. John Hopkins Medicine
This page discusses radiation therapy and common side effects.
|Radiation Therapy for Cancer
April 23, 2012. U.S. National Institutes of Health, National Cancer Institute
Here, you can read about different types of radiation therapy, including external beam.