By Melissa Knopper
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.
