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SNM: Brain scans shed light on risk for Alzheimer's

by Brendon Nafziger, DOTmed News Associate Editor | June 09, 2010
New PET agents may help
detect Alzheimer's earlier
Brain scans could help detect Alzheimer's early, possibly to help doctors treat the ailment before permanent damage is done; and new agents could make the scans more accessible to patients, according to a spate of research shared Monday at the SNM's annual meeting in Salt Lake City.

Based on post-mortem studies, most researchers believe the build-up of protein fragments known as beta amyloid deposits in the brain leads to, or at least is deeply linked to Alzheimer's, an eventually fatal dementia, explained Chester A. Mathis, the director of the radiology department at the University of Pittsburgh.

"There seems to be a correlation between people with cognitive deficits and the amount of plaques and neurofibrillary tangles," Mathis told DOTmed News by phone. "But are they really the cause of the death? Or just markers, like gravestones, that just mark the death?"

Whether killers or victims of circumstantial evidence, the plaque deposits might still give clues to the early discovery, and thus treatment, of the disease, thanks in part to one of Mathis' discoveries.

Mathis, who received this year's Aebersold Award for advances in basic nuclear medicine science at SNM on Sunday, helped discover the 11C Pittsburgh Compound-B, or PiB.

PiB is a PET tracer that binds to beta amyloid deposits, and might help doctors detect the disease before irreversible dementia sets in.

In one study presented at the SNM meeting Monday, led by Dr. Christopher Rowe of Austin Hospital in Melbourne, Australia, researchers followed 188 patients-- some with Alzheimer's, some with mild cognitive impairment, and some healthy controls -- between around 20 months to three years to see if PET brain scans picking up plaque deposits could predict later developments of dementia.

Rowe and his team found those with a positive scan for beta amyloid build-up had a 66 percent chance of developing dementia. Only one person with a negative scan went on to develop dementia.

"She was an 85-year-old woman who was frail," Rowe told DOTmed News, and the dementia might not have been Alzheimer's related. "If you have mild cognitive impairment and a positive scan, you have a 13 times greater risk to develop to full-blown dementia in two years," he said.

However, while high PiB binding in those with cognitive impairment was associated with increased risk for Alzheimer's, the change in beta amyloid load wasn't associated with cognitive decline.

Also, showing high PiB binding is rather common as we age, so a positive scan doesn't necessarily mean you should be worried. In the study, only 14 percent of healthy subjects with high PiB levels developed mild cognitive impairment or Alzheimer's after a year and a half, and around 21 percent after three years.