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Intensity-modulated Radiation Therapy (IMRT)

Brigham and Women’s Hospital offers Intensity-modulated radiation therapy (IMRT), a state-of-the-art radiation treatment technique.

What is Intensity-Modulated Radiation Therapy (IMRT)?

Intensity-Modulated Radiation Therapy (IMRT) is a cancer treatment that matches radiation intensity to the shape of a tumor. IMRT allows doctors to customize the radiation dose by varying the amount of radiation given to different parts of the treatment area. This is done in highly accurate, three-dimensional detail, according to the shape, size, and location of the tumor, and helps minimize radiation exposure to normal surrounding organs.

How does Intensity-Modulated Radiation Therapy (IMRT) work?

  • Multiple beams are positioned at various points around the patient
  • Beams are divided into a grid-like pattern, separating the one big beam into numerous smaller "beamlets"
  • Special software is used to determine the best pattern of beamlets to use, delivering optimal amount of radiation to the tumor while sparing normal organs as much as possible

What are the advantages of Intensity-Modulated Radiation Therapy (IMRT)?

  • Delivers a higher dose of radiation to the tumor, with less damage to nearby healthy tissue
  • Shapes the radiation intensity to uniquely match radiation to the size and shape of the tumor
  • Is commonly used in cancers of the head and neck where many critical structures that may be near the tumor, such as the spinal cord and the salivary glands, must be avoided
  • Has been shown to be a beneficial treatment for prostate cancer because it significantly decreases the risk of rectal bleeding and provides the opportunity for dose escalation to decrease the likelihood of developing metastatic prostate cancer

Volumetric Modulated Arc Therapy (VMAT) is a type of IMRT commonly used by our department.

What is Volumetric Modulated Arc Therapy (VMAT)?

  • A type of Intensity-Modulated Radiation Therapy
  • A linear accelerator rotates around the patient while delivering radiation at the same time
  • This process increases the number of angles and decreases the high dose radiation to normal tissues
  • Often used for head and neck cancers, brain tumors, GI cancers, prostate cancers, and lung cancers
  • For example, IMRT improves coverage of the prostate gland and head and neck cancers while reducing the radiation dose to organs at risk, such as the rectum, bladder and salivary glands

How does Intensity Modulated Radiation Therapy (IMRT) compare to other treatments?

We now have randomized controlled trials comparing IMRT to the previous standard, which was 3-dimensional (3D) conformal radiation therapy (CRT). IMRT results in significantly less rectal and bladder side effects for prostate cancer, as well as less changes to the salivary glands in patients with head and neck cancers.

Are there special preparations needed for Intensity Modulated Radiation Therapy (IMRT)?

  • Some cancers such as prostate cancer or abdominal tumors cannot be seen well on the x-ray imaging
  • In these situations, we may implant gold seeds as fiducial markers that can be seen when setting up the daily radiation to ensure accurate targeting
  • This allows very precise targeting of the tumor allowing us to spare more healthy tissue

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