New imaging techniques are helping researchers predict the course of Alzheimer's disease and show preliminary evidence that the affected brain cells are not dead but are merely "idling," researchers at the National Institute of Aging reported last week.

Researchers say that this finding suggests that in the early stages of the disease the cells are alive and could one day be reactivated by drugs.

"It's rather optimistic," said Stanley I. Rapoport, chief of NIA's laboratory of neuroscience.

In addition, Rapoport said, he and his colleagues also have been able to predict the course of illness in 90 patients with early signs of Alzheimer's disease using positron emission tomography (PET).

PET scanners are sophisticated machines that measure the amount of energy used by brain cells and are a way of calculating how well those cells are functioning. In the early stages of Alzheimer's disease, brain cells use less energy and important differences appear in energy use between the left and right sides of the brain.

By looking at these early changes, it is now possible "to predict what the deficits will be one to three years down the line," said Rapoport.

This, he says, will help doctors treat the disease.

For example, patients who exhibited greater changes in the right side of the brain experienced earlier disorientation, such as difficulty finding their way home, but retained the ability to speak and communicate longer, according to Rapoport. Those who had greater left-brain changes had much more difficulty talking but were less disoriented, Rapoport said.

An estimated 1.3 to 1.8 million Americans 65 years and older suffer from Alzheimer's disease, a degenerative brain disorder that causes progressive dementia.

No one knows exactly what causes the illness, although studies suggest that something goes awry with the brain cells' ability to produce key neurotransmitters -- chemicals that allow communication between cells.