May 9, 1997

New 3-D imaging device pinpoints location of tumors

New 3-D imaging device pinpoints location of tumors

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Dr. Anthony Cmelak, assistant professor of Radiation Oncology, and medical physicist Kim McGee work with VUMC's new 3-D imaging equipment, which helps map the locations of tumors.

A new three-dimensional imaging device is enabling VUMC physicians to more accurately map out the precise locations of cancerous tumors.

This ability to better visualize tumors and surrounding tissues allows for more efficient and beneficial use of radiation therapy by steering radiation away from surrounding tissues.

"In 20 to 30 percent of our patients, we have significantly changed the treatment plan using the three-dimensional imaging technology," said Dr. Anthony J. Cmelak, assistant professor of Radiation Oncology.

Visualizing the tumor in three-dimensions recently allowed VUMC physicians to treat a tumor that was pressing against the eye of a patient. Standard treatment might have damaged both of the patient's eyes had it not been for the new device, Cmelak said.

With the help of this system physicians were able to plan a treatment route that did not damage the patient's working eye, yet still treated the tumor.

"This is an example of how we are able to spare the patient undue damage because of this new technology," said Shai Levit, a member of the medical physics treatment planning team.

Accurately mapping out the different parts of the body with the new device gives doctors an added edge in knowing what kinds of problems might be encountered during treatment.

For example, if a patient has a tumor in the brain near Wernicke's area, which is responsible for language ability, the physician could expect some problems with speech. If the patient then displays problems with vision or memory, the physician knows that there is something else going on in another area.

"The great thing about this technology is that doctors can see all of these areas of the brain, which they could not do by using normal x-rays," said Levit.

Another component of this technology is that it allows doctors to concentrate higher doses of radiation within a smaller area.

"What we are finding is that previously we were actually missing portions of tumor in a number of patients. By using this device, we have the ability to increase the doses to the tumor while decreasing the amount of treatment to healthy tissue," said Cmelak. "We therefore gain a substantial therapeutic advantage."

It takes two separate systems to produce the 3-D images. One is a CT simulator, which receives the images from a CT scanner. The second is a treatment planning computer which allows doctors to direct the radiation beam through healthy tissues to the site of the tumor.

The computer allows visualization of the tumor in three dimensions, as well as a 'beam's-eye-view' of treatment x-rays as they penetrate a patient's body. The result is a graphic representation of the body that allows physicians to quickly assess treatment options.

Obtaining the new 3-D treatment planning system was a cooperative effort of both the Radiation Oncology and Radiology teams.

"We used to require big stacks of plain x-rays, MRIs and other scans to measure the location of the tumor," Levit said. "Now, the doctors can take precise measurements from the three-dimensional system and reconstruct the tumor on the computer, which is much more accurate."