Intensity Modulated Radiation Therapy (IMRT)

Overview

Multiple IMRT beams deliver high-dose radiation

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IMRT treatment plan for treating cancer in the head

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Intensity-modulated radiation therapy (IMRT) is an advanced type of three-dimensional radiation that conforms to the shape of a tumor. It uses hundreds of small radiation beams of varying intensities to precisely radiate a tumor. The radiation intensity of each beam is controlled, and the beam shape changes hundreds of times during each treatment. As a result, the radiation dose bends around healthy tissues in a way not possible with other techniques.

Mayo Clinic doctors usually give a series of IMRT treatments over four to eight weeks. The number of treatments depends on the size, location and type of cancer; the person's health; and the other cancer therapies taken. Doctors use CT scans, MRI scans and positron emission tomography (PET) scans to create a treatment plan that targets just the tumor. During treatment, special head frames or supports may keep the body from moving.

Some organs, such as the prostate, move due to normal changes in the bladder and rectum. Doctors may place gold seeds into the prostate to track prostate movement and ensure more precise targeting of the tumor.

Each year, Mayo Clinic doctors treat more than 1,000 people who have advanced and recurrent tumors using IMRT. At Mayo Clinic, IMRT involves close cooperation among a team of specialists — including cancer specialists skilled in radiation therapy (radiation oncologists), radiation therapy specialists (dosimetrists), oncology nurses and other specialists.

Conditions treated with IMRT

Radiation oncologists consider IMRT to be ideal for prostate cancer as well as cancerous and noncancerous tumors of the head and neck and other organs that lie near the optic nerves, brain, salivary glands, bladder, rectum, small bowel, kidneys, liver, lungs and spinal cord.

Advantages of IMRT

Advantages of IMRT, compared to traditional radiation therapies, include:

• Minimal radiation to healthy surrounding tissue
• Decreased risk of harming normal cells
• Higher radiation dosage to cancer cells
• Precise radiation distribution
• Increased chance of destroying cancer cells

Like other treatments, IMRT carries some risks. Mayo Clinic doctors discuss the benefits and risks with people to help them decide on a treatment.