The device, called multifrequency transcranial Doppler (MTCD) ultrasound, also allows physicians to distinguish between blood clots and gas bubbles that often enter the bloodstream during heart procedures and surgery.
Transcranial Doppler ultrasound uses sound waves transmitted through the skull to create images that allow physicians to study blood flow through vessels in the brain. The conventional transcranial Doppler generates sound waves at just one frequency. The MTCD device generates sound waves at two frequencies.
"The distinction is important because a solid clot reflects back more ultrasound signal at the higher frequency, but gaseous bubbles reflect back more signal at the lower frequency," says study author David Russell, M.D., professor of neurology at The National Hospital, Oslo, Norway.
The technology, available in Europe but not in the United States, could greatly reduce one of the most common complications of coronary bypass surgery. In 1999, 355,000 Americans underwent bypass surgery, according to the American Heart Association. Russell says as many as 50 percent of coronary bypass patients experience cognitive decline such as memory loss. Tiny clots that cause minor, symptomless strokes during the surgery lead to this impairment. Conventional monitoring doesn't detect those tiny clots, he says.
"In the past, we could detect something entering the arteries of the brain, but we could not tell if it was a very small gas bubble or blood clot. It was like a policeman who could detect a speeding vehicle but didn't know whether it was a small car or a larg
Contact: Bridgette Mc Neill
American Heart Association