[MOL] Gel'phantoms' advance imaging research.... [01626] Medicine On Line

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[MOL] Gel'phantoms' advance imaging research....

Thursday, July 27, 2000
Gel 'phantoms' advance imaging research

CHICAGO, Jul 26 (Reuters Health) - When perfected, researchers believe a process called gel dosimetry will help physicians better understand and use modern imaging techniques such as MRI and CT scans. It may also reduce the risks of radiation therapy used to treat cancer patients.

Scientists are making progress with gel dosimetry, but they are not yet ready to take the promising technique into the clinical setting, according to researchers who spoke here this week during a mini-symposium at the World Congress on Medical Physics and Biomedical Engineering.

Gel dosimetry offers several advantages, said Dr. Lars Olsson, of M.D. Anderson Cancer Center in Houston. First, it is a non-invasive technique that works for CT, MRI and ultrasound. It also gives physicians a 3-dimensional view of radiation therapy's impact on the body. "It's data you can really rely on," Olsson said. "It gives a level of precision."

The procedure involves filling a model of a body part, such as a head, neck or breast, with a gel mixture. The technician then gives the gel-filled model--or "phantom"--the same treatment planned for the patient to gauge its effectiveness. Radiation alters the chemical structure of the gel, so the changes appear when scientists view a cross section of the phantom on the computer screen.

Physicians have used phantoms for several years, but they were unable to get 3-D views until researchers began using polymer gels in the late 1980s, Olsson said. Some scientists prefer to use Fricke gels or xylenol orange, a chelation agent. Like the human body, the gels are mostly made of water, said Dr. Clyde Baldock, who studies gel dosimetry at Queensland Technical University in Australia. The substance includes gelatin and other ingredients. Several labs have had good results by adding PVA to the mix, Baldock said.

In the past five years, researchers have made progress with gel dosimetry, Olsson said, but it is still not perfect. "We have to be sure we can make it a reliable technique," he added.

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