Doctors will soon start the first human tests of a new technique using infrared light that could allow them to monitor a patient's brain function, much as they now monitor heart function.

Dr. Patrick McCormick, a neurosurgeon at Henry Ford Hospital in Dearborn, Mich., said the Food and Drug Administration recently granted researchers there permission to test the technique, known as infrared spectroscopy, on 20 critically ill patients.Using a light source and sensor that is about 1 inch square, the device shines invisible infrared light into the patient's skull. The way the light bounces back, after some absorption by blood and other molecules in the brain, gives doctors important information about how the brain is functioning.

"This information will be extremely useful in treating patients with brain injury caused by stroke or trauma," said Dr. Manuel Dujovny, also a neurosurgeon at Henry Ford.

McCormick said the technique is inexpensive, non-invasive and can be used continuously to monitor oxygen levels, the amount and flow of blood, and energy use in the brain. "This is the wonderful thing about the technique," McCormick said.

"When a patient is critically ill, we can monitor their heart, their lungs, their kidneys, but never before have we been able to monitor their brain in this way," McCormick said.

The light pattern bouncing back to the fiber optic sensor is tranferred to a computer which translates it and sends the information to a screen. About 5 percent of the brain can be observed from one sensor, and several sensors can be used at once, McCormick said.

He said unlike other brain imaging techniques, like magnetic resonance imaging or tomography, infrared spectroscopy "is not really creating an image of the brain, but of the optical density of chemicals" in the brain that reveal how it is functioning.

McCormick said this would allow detection of dropping blood flow to the brain "to give the earliest possible warning that the brain is not receiving enough oxygen or blood and appropriate therapy can be started to prevent damage" such as strokes.