Sarah Goodwin

Kathi Ovnic
Holly Korschun
January 14, 1999


Emory University medical physicists have helped develop a high tech, computerized method of delivering radiation therapy to cancer patients that better targets the cancer, without damaging surrounding tissue. Intensity Modulated Radiation Therapy, or IMRT, uses a computer program to determine where and how radiation should be directed to a tumor.

"The limiting factor in traditional radiation delivery is the amount of radiation that healthy tissue around the tumor can take and still regenerate," says Lawrence Davis, M.D., chair of the department of radiation oncology at Emory. "It has been difficult to treat the tumor with enough radiation to kill it without having serious side effects from how much radiation the surrounding tissue is receiving. With computerized targeting of the radiation, less healthy tissue will be affected."

Joseph Ting, Ph.D., director of medical physics and associate professor of radiation oncology, has been studying the use of IMRT treatments for a treatment known as "electronic tissue compensation" in lung, breast, brain, head and neck cancers. Tissue compensation is a way to balance radiation delivery to focus energy on the tumor and avoid surrounding tissue.

In traditional radiation therapy, lead sheets, called physical compensators, are used to block the radiation going to surrounding healthy tissue. But the effectiveness of physical compensators depends on the precision of therapists placing them and the relocation of the patient to the same position for each treatment session.

Using the computer program to electronically focus the radiation beam avoids human error in positioning the compensators, excess trips to the treatment room between doses to change compensators, and the cost and time associated with making the lead sheets, blocks and other compensation devices.

Another concern with traditional therapy is getting the correct dosage to cancer sites. IMRT uses a "multi-leaf" collimator to send non-uniform doses of radiation to the tumor. Because the body is three-dimensional, the flat or uniform doses of radiation traditionally used in treatment are absorbed differently by different parts of the body, making it difficult to treat angular areas such as the head and neck and the breast. The dosage set up by IMRT is non-uniform, using up to 120 individually adjusted metal "leaves" that shape the beam to the varying shape of the organ. This enables the radiation oncologist to raise the dosage of the radiation beam to levels that will more effectively kill the tumor without raising the amount that will hit healthy tissue.

Currently The Emory Clinic is one of the few treatment centers in the nation to offer IMRT treatment. For more information on IMRT, contact Diane Cassels at 404/778-4012 or Emory Healthconnection at 404/778-7777.

For more general information on The Robert W. Woodruff Health Sciences Center, call Health Sciences Communication's Office at 404-727-5686, or send e-mail to

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