Alzheimer Disease Plaques Seen With Conventional MRI in Animal Model for the First Time

Monday, July 28, 2008 General News
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CHICAGO, July 27 For the first time, scientistshave captured images of brain lesions similar to those found in Alzheimer'sdisease using clinical-grade MRI in an animal model of the disease, accordingto research reported today at the Alzheimer's Association's 2008 InternationalConference on Alzheimer's Disease (ICAD 2008), in Chicago.

These lesions, known as amyloid plaques, have been "imaged" previouslyusing very high power MRI scanners that are only used on animals, and alsowith PET scans combined with specialized marker chemicals. This is the firsttime images of plaques were captured with conventional, clinical strength MRI.

Two other studies reported at ICAD 2008 use MRI and advanced computeranalysis to bring us closer to early identification of Alzheimer's, perhapseven before symptoms are evident.

MRI technology is more widely distributed and relatively less expensivethan other imaging technologies. In addition, it doesn't expose people toradiation, as do the "high energy" imaging approaches.

"As we get closer to the development of therapies that can slow or evenstop the progression of Alzheimer's, earlier detection of the disease becomescrucial for early intervention," said William Thies, PhD, vice president ofMedical and Scientific Relations at the Alzheimer's Association. "Earlyevaluation and diagnosis is also important because some Alzheimer's-likesymptoms can be reversed if they are caused by treatable conditions, such asdepression, drug interaction, or thyroid problems. If it is Alzheimer's, earlydiagnosis gives the person and their family an opportunity to build the rightmedical team, get access to existing medications, find helpful programs andservices, and plan for the future. Plus, there is the opportunity toparticipate in studies of experimental drugs or other disease modifyingtreatments."

"As we search for ways to identify Alzheimer's early, these MRI studiesshow that researchers are moving closer to accurate early detection of thedisease, and that we may soon be able to use this technology to determine whois at greater risk," Thies added.

MRI Scans Show Images of Amyloid Plaques in Rabbit Model

Definitive diagnosis of Alzheimer's currently happens at autopsy bydemonstrating the presence of characteristic brain lesions, including amyloidplaques. The ability to non-invasively show amyloid plaque levels in livingpeople could markedly improve the diagnosis and treatment of people withAlzheimer's.

John Ronald, a Ph.D. candidate in Medical Biophysics, along with BrianRutt, PhD, and colleagues at the Robarts Research Institute and University ofWestern Ontario, London, Ontario, Canada, used clinical strength MRI scannersto take brain images from rabbits that had been fed a high cholesterol dietfor more than two years. These animals form amyloid plaques in their brains.

According to the researchers, the MRI scans revealed distinct signal voids- black spots - in several brain areas including the hippocampus, which isvery important for memory. Autopsy examination revealed that the void areasreflected the presence of small clusters of amyloid plaques. Each cluster hadhigh levels of iron, which the researchers say caused the MRI signal voids;these signal voids were not found in animals fed a normal diet.

"Although some of the technology used to generate these images wasdesigned specifically for rabbits, this preliminary discovery hints at thepromise of using clinical MRI scanners to visualize plaques in people withAlzheimer's," Ronald said. "Extension of these technologies to living animalsis practical, and should allow us to study the course of Alzheimer's inanimals over time."

"We have customized this MRI scanner in very important ways formicroimaging. Particularly, we have added special hardware that allows thescanner to clearly detect structures smaller than 50 micr

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