July 28, 2008

MRI Captures Alzheimer's Lesions

SUNDAY, July 27 (HealthDay News) -- Scientists are reporting that they have captured images of brain lesions in rabbits similar to those found in people with Alzheimer's disease using conventional MRIs.

Amyloid plaques, which accumulate in the brain and are a hallmark of Alzheimer's, have been captured before through extra-high-power MRI scanners meant for use in animals and with PET scans.

But in this case, lead author John Ronald and his colleagues used regular-strength MRI scans. "We souped up a clinical-grade MRI for the ability to really detect very small . . . structures," said Ronald, a doctoral candidate in the medical biophysics department at the University of Western Ontario Imaging Labs and Robarts Research Institute in London, Ontario, Canada.

The scans revealed "little signal voids within the MR image" caused by iron accumulation apparently resulting from the animals' high-cholesterol diet, Ronald explained. Subsequent autopsies showed that the voids corresponded with areas with amyloid plaque clusters.

The research was expected to be presented Sunday at the International Conference on Alzheimer's Disease in Chicago.

Although the scanners employed in the study are routinely used for humans, it's unclear what the results might actually mean for humans. But some hope is pinned on magnetic resonance imaging technology, which tends to be more available and less expensive than many other imaging systems.

"This technology is not directly translatable to human imaging, but we feel this might inspire other people to consider this approach," Ronald said. "We're starting to explore the building of new hardware and the ability to potentially do this one day in humans."

"There has been a lot of effort to look at atrophy or shrinkage of the brain with MRI scans in patients with Alzheimer's disease, and we do know that the brain shrinks as disease progresses," said Dr. Scott Turner, incoming director of the Memory Disorders Program at Georgetown University Medical Center in Washington, D.C., "This is a new approach, [but] it's much easier to do when the brain is smaller such as in a mouse or a rabbit."

Researchers have long been looking for ways to identify and diagnose the disease earlier in its progression.

"There is no way to diagnose a patient until after they die, so patients and families are left with the uncertainty of whether they have Alzheimer's or some other form of dementia," Ronald explained.

In related news also being presented Sunday at the conference:

• Researchers at the Mayo Clinic in Rochester, Minn., confirmed that a new MRI analysis algorithm could capture the severity of another hallmark of Alzheimer's disease, neurofibrillary tangles, in the brain. The method could one day be used for earlier diagnosis of the disease.
• University of Pennsylvania investigators found that "Alzheimer's-like patterns" of brain atrophy or shrinkage were more common in individuals over the age of 80. These patterns also developed faster the older an individual became. It's unclear how these patterns might correlate with actual cognitive function, but researchers are hopeful that this may provide a way to detect early brain changes related to Alzheimer's.
• Two more Mayo Clinic studies concluded that multiple different imaging techniques, such as MRI, magnetic resonance (MR) spectroscopy, and 11C Pittsburgh Compound B each contribute information about a person's cognitive function. Using the techniques together would give a more complete picture than using each alone.

More information

Visit the Alzheimer's Association for more on this condition.

SOURCES: John Ronald, Ph.D. candidate, department of medical biophysics, University of Western Ontario Imaging Labs and Robarts Research Institute, London, Ontario, Canada; Scott Turner, M.D., Ph.D., incoming director, Memory Disorders Program, Georgetown University Medical Center, Washington, D.C.; July 27, 2008, presentation, International Conference on Alzheimer's Disease, Chicago
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