Invisible light and special goggles may improve brain tumor surgery

03/26/04

ORLANDO -- Some day "night vision" goggles and beams of near infrared light may be able to detect tiny tumors and areas of cancerous tissue in the brain that surgeons can't normally see, say investigators at The University of Texas M. D. Anderson Cancer.

They say their advance, successfully tested in animals, is designed to help neurosurgeons define tumor "margins" -- the area where a tumor ends and normal tissue begins -- when they operate on patients with brain tumors.

"No one can determine tumor margins in brain tissue adequately right now, but our hope is that the emerging technology of near-infrared fluorescence optical imaging will provide this crucial information in real time to surgeons, as an operation is under way," says investigator Shi Ke, M.D., an instructor in the Department of Experimental Diagnostic Imaging at M. D. Anderson.

Ke is presenting results of an imaging probe that allowed detection of small tumors in the brain at the annual meeting of the American Association for Cancer Research.

When perfected, near infrared optical imaging of brain tumors may offer a "safe, non-invasive and highly sensitive" method that can improve surgical treatment, says Ke.

Although neurosurgeons now use diagnostic scans that pinpoint where tumors are prior to an operation, once the skull is open, soft brain matter shifts, making it difficult to know where tumor tissue ends.

Life expectancy of brain tumor patients is tied to the amount of tumor that remains, according to Ke, Research reported recently by neurosurgeons at M. D. Anderson found that if 98 percent of a glioma brain tumor is removed, patients survive for more than a year. If 95 percent of the tumor is removed, survival decreases by more than four months.

Although several research teams around the country have been experimenting with similar devices, collectively known as near-infrared (NIR) optical imaging, no one has tried it before in brain tumors, says Ke.

To make it work for brain tumors, Ke and others in a research team lead by Chun Li, M.D., associate professor in the Department of Experimental Diagnostic Imaging, developed a special kind of dye that can find its way to tumors inoculated in the brain. They chose a dye found from an in vivo screening process that binds to many human tumors as well as in gliomas, but not to normal tissue. Then, using a NIR camera developed by scientists at Texas A & M University, they tested the ability of the dye to pick up tumors as they grew in laboratory mice.

Light in the near-infrared wavelength spectrum easily penetrated the skulls of the animals to "excite" the dye, and the emitted fluorescent signal was then captured by a CCD camera. The tumors shone with a brighter light than the normal brain tissue around them, says Ke.

The study is an important proof-of-principle that such a device can detect brain tumor margins and small tumors, he says. Now, investigators are testing NIR optical imaging in the earliest stages of brain tumor development, and they also plan to test its ability to distinguish melanoma, endometrial and prostate tumors.

Source: Eurekalert & others

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