Intensity Modulated Radiation Therapy



Radiation therapy uses radiation to kill cancer cells and shrink tumors.

Intensity modulated radiation therapy (IMRT) uses radiation beams of different intensities. The beams deliver appropriate doses of radiation to the tumor and reduce the dose to nearby healthy tissue.

Radiation of Tumor

Radiation of Tumor
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Reasons for Procedure    TOP

Radiation therapy works to destroy or shrink the tumor to eliminate or prevent the spread of cancer. It can also be used to relieve symptoms caused by the tumor, such as pain and bleeding. Compared with conventional radiation therapy, IMRT can safely deliver greater doses of radiation. The higher dose may also improve the success of the treatment.

Possible Complications    TOP

Some normal cells will be damaged with radiation. The goal of radiation therapy is to kill as many cancer cells as possible while limiting damage to healthy cells.

IMRT is generally associated with fewer side effects than conventional radiation therapy. Side effects vary from person to person, depending on the location of your cancer. Some people experience no side effects at all. General side effects of radiation therapy may include:

  • Fatigue
  • Skin changes
  • Hair loss
  • Loss of appetite
  • Specific side effects associated with the area of the body being treated

Although uncomfortable, the side effects associated with radiation therapy are usually not serious. They can be controlled with medication and diet. Your radiation oncologist can explain the side effects you are likely to experience and help determine the best strategies to manage them.

What to Expect    TOP

Prior to Procedure

Planning for IMRT is complex and generally takes 2-5 days. Planning may include:

  • Physical exam
  • Imaging tests to identify exactly where the radiation beams will be focused. Some tests may use contrast material to highlight structures. These may include:
  • Marking the locations on the skin where the radiation will be focused to guide the therapist
  • Being fitted for a localization device, such as a mask or body frame, to help target accuracy
  • Using ultrasound or implanted markers to track the position of the tumor

Description of the Procedure

Using the marks made on your skin as a guide, the radiation therapist will position you on the treatment table. Films or ultrasound may be used to check the accuracy of the treatment setup. The therapist leaves the room to control the movements of the radiation machine. The treatment delivers radiation in a 3-dimensional manner. This will help to conform as closely as possible to the shape of the tumor. The healthy tissue receives smaller doses of radiation than the tumor.

You will be asked to remain still during the radiation treatment. You may breathe normally. In general, you will not feel or sense anything during treatment. However, the machine can be stopped if you feel sick or uncomfortable. The therapists will be observing you with a monitor. You will be able to communicate to them should you need to.

Immediately After Procedure    TOP

You will be able to leave and resume your normal daily activities. Receiving IMRT does not make you radioactive. You do not need to avoid being around other people because of the treatment.

How Long Will It Take?    TOP

Each session will take 15-30 minutes. Patients are typically scheduled for IMRT 5 days per week for 4-8 weeks.

How Much Will It Hurt?    TOP

Holding one position may become a little uncomfortable, but it is not painful.

Post-procedure Care    TOP

During treatment, your doctor will want to see you at least once a week. You may have blood tests or other studies performed.

After your treatment is completed, you will come in for regular visits to monitor for side effects and healing and check for signs of recurrent disease. You may require further testing, medication, or rehabilitative treatment.

Call Your Doctor    TOP

Call your doctor if any of these occur:

  • Persistent pain
  • New or unusual lumps, bumps, or swelling
  • Nausea, diarrhea, vomiting, or loss of appetite
  • Unexplained weight loss
  • A cough, sore throat, or fever that does not go away
  • Unusual changes to skin, including rashes, bleeding, or bruising

If you think you have an emergency, call for emergency medical services right away.


American Cancer Society
Radiology Info—Radiological Society of North America


Canadian Association of Radiologists
Canadian Cancer Society


IMRT. International Radiosurgery Support Association website. Available at:
...(Click grey area to select URL)
Accessed March 29, 2018.
Intensity-modulated radiation therapy (IMRT). Radiological Society of North America Radiology Info website. Available at: Updated January 25, 2017. Accessed March 29, 2018.
Radiation therapy. American Cancer Society website. Available at: Accessed March 29, 2018.
Radiation therapy and you: Support for people with cancer. National Cancer Institute website. Available at: Updated October 2016. Accessed March 29, 2018.
Radiation therapy for cancer. National Cancer Institute website. Available at: Accessed March 29, 2018.
Last reviewed March 2018 by EBSCO Medical Review Board Mohei Abouzied, MD, FACP
Last Updated: 3/18/2013

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