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Intensity Modulated Radiation Therapy (IMRT)

Intensity Modulated Radiation Therapy (IMRT) is another type of external radiation therapy that uses thousands of radiation “beamlets” from many different angles to deliver radiation to your tumor. These deliver a precisely focused dose of radiation to the prescribed target while minimizing damage to surrounding, normal tissue.

How It Works

IMRT begins with a simulation. Your radiation oncologist will use advanced imaging, typically CT or PET/CT scans, to create a detailed view of your internal organs and tumor. Your radiation oncologist and treatment team then decide on the total dose of radiation that you are to receive. A sophisticated computer then determines the number of beams and angles to achieve this dose. The number and intensity of thousands of tiny “beamlets” will be delivered to your tumor, following the pattern and instructions automatically received from the system's computer.  Many times IMRT is used in an effort to increase the dose to the tumor but significantly reduce exposure to healthy tissues that may be very close or directly up against the tumor.

Treatment Process

It is very important that you lie in exactly the same position for each treatment session. You may be custom-fitted for a mold that will be used to position you correctly on the treatment table. You may also be tattooed with freckle-like marks that will help the radiation therapist precisely target the radiation beams.          

During each IMRT session you will lie on the treatment table and your radiation therapist will use sophisticated imaging to confirm your exact position. Minor adjustments may be made to the table to ensure exact targeting of the tumor. The radiation delivery system then moves in a circular motion around you; delivering beams from different angles and intensities, shaping them around the tumor. Each treatment session lasts from 10 to 30 minutes. Typically, you will be scheduled for five sessions a week for five to eight weeks. The sessions are pain-free and require no sedation so you can return to your normal activities right away.


  • Higher and more effective radiation doses can safely be delivered to tumors with fewer side effects
  • Reduced treatment toxicity

Types of Cancer Treated with IMRT

IMRT may be used to treat many areas including:

The Cancer Center operates in partnership with Upstate Cancer Center.