MRIs show promise for early Alzheimer's diagnosis

By Julie Steenhuysen
28 july 2008--Researchers have used magnetic resonance imaging scans to locate Alzheimer's-like plaques in rabbits, bringing researchers a step closer to being able to diagnose the disease using ordinary MRI equipment.
"Although some of the technology used to generate these images was designed specifically for rabbits, this preliminary discovery hints at the promise of using clinical MRI scanners to visualize plaques in people with Alzheimer's," John Ronald of Ontario's Robarts Research Institute said in a statement.
The study, unveiled at the International Conference on Alzheimer's Disease in Chicago on Sunday, was one of several showing how widely available MRI scans could be used for early diagnosis of the brain-wasting disease.
The study marks the first time researchers have been able to "see" brain plaques using conventional MRI scanners. Currently, high-powered MRI scanners have been able to spot them in animals, and PET scanners using special marker chemicals have worked as well.
Currently, an autopsy is the only sure way to confirm Alzheimer's disease, by identifying the brain lesions such as amyloid plaques that characterize the disease. Doctors typically rely on a series of tests to give them a good idea of whether someone has Alzheimer's.
Researchers in the Canadian study fed rabbits a high-cholesterol diet for two years, which caused them to form amyloid plaques in their brains. Scans of these rabbits revealed void areas or black spots in several areas including the hippocampus, an important memory center in the brain.
Autopsies found small clusters of amyloid plaques in these void areas, not found in rabbits fed a normal diet.
"This may be used for animal imaging, but potentially down the road it may be used for human imaging," Ronald told a media briefing.
Dr. Jeffrey Kaye of the Oregon Health & Science University in Portland, who moderated the briefing, said the study has promise but the jump between rabbits and humans may not be effortless. He said researchers using special high-field MRI magnets can already see amyloid plaques in mice, but so far have not been able to see them in human brains.
"I have to believe it will be solved," Kaye added.
In a separate study, researchers at the Mayo Clinic in Rochester, Minnesota, said they were able to use a computer program to analyze information on MRI scans that could distinguish between normal and Alzheimer's brains with 90 percent accuracy.
The program, known as STAND, measures the degree of atrophy in a person's brain.
The researchers compared data gathered from 101 people who had an MRI within four years of their death to data gathered after they died by a test known as Braak staging, which measures the severity of fibrous tangles in the brain.
"This study shows that information extracted from MRI scans can accurately capture the severity of Alzheimer's tangle pathology," Prashanthi Vemuri, who presented the results, said in a statement.
A third group from the University of Pennsylvania in Philadelphia, using a new computer-based image analysis technique, was able to find Alzheimer-like activity in the brains of elderly people who had normal cognitive capabilities, and in a group with mild cognitive impairment.
While more study is needed to understand the findings, they hope the tools will help in the search for early brain changes that signal the start of Alzheimer's.
"These MRI studies show that researchers are moving closer to accurate early detection of the disease, and that we may soon be able to use this technology to determine who is at greater risk," William Thies of the Alzheimer's Association said in a statement.