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Tracking Alzheimer's: New tool would help measure plaque deposits in patients

By Jamie Talan, Newsday

January 22, 2004

A new tool allows doctors to detect and measure plaque deposits in the brains of living Alzheimer's patients, a major advance that doctors say could help in diagnosis and research.

Until now, the amyloid plaques, considered the hallmarks of Alzheimer's, could be measured only through visual inspection at autopsy.

"It will be an incredible tool," said Dr. Brad Hyman, professor of neurology at Harvard Medical School and Massachusetts General Hospital . "In addition to diagnosis, it would give us a good way to test whether preventing amyloid deposition works to slow or block the disease process."

A study designed to test the imaging device in humans was published today in the Annals of Neurology. Dr. William Klunk of the University of Pittsburgh Medical Center has spent years looking for a substance that could be used to image amyloid.

The classic amyloid protein-filled plaques have fueled much of the scientific work for almost 20 years, and having an image of this plaque in the living patient gives doctors a window into the biochemical process under way in the mind-robbing illness that affects an estimated 4.5 million Americans living with the disease today.

Klunk and co-inventor Chet Mathis, professor of radiology at the University of Pittsburgh School of Medicine, finally settled on thioflavin-T, a dye that crosses into the brain and stains amyloid. After chemical modifications, they came up with a more powerful derivative. With this substance in hand, they contacted an organic chemist, Bengt Langstrom at Uppsala University in Sweden, to test the imaging substance in nine volunteers who served as controls and 16 patients diagnosed with mild Alzheimer's.

The dye is combined with a radioactive marker that highlights the amyloid on a brain scan. Mathis said one of the control patients showed a small amount of amyloid deposit. The man, in his 70s, was just beginning to show vague symptoms of cognitive decline.

The next step is to continue testing the imaging in more volunteers - patients and healthy people.