Several studies show MRI is closing the distance on earlier Alzheimer diagnosis

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Scientists have captured images of brain lesions similar to those found in Alzheimer's disease using clinical-grade MRI in an animal model of the disease, according to research reported at the Alzheimer's Association's 2008 International Conference on Alzheimer's Disease (ICAD 2008) in Chicago.

The lesions, or amyloid plaques, have been imaged previously using high power MRI scanners that are only used on animals, and also with PET scans combined with specialized marker chemicals, according to the study’s researchers.

According to another study presented during ICAD 2008, John Ronald, a PhD candidate in Medical Biophysics, along with Brian Rutt, PhD, and colleagues at the Robarts Research Institute and University of Western Ontario in Canada, examined MRIs from rabbits that had been fed a high cholesterol diet for more than two years to form amyloid plaques in their brains.

The researchers said that the MRI scans revealed distinct signal voids in several brain areas, which, after autopsy, revealed that the void areas reflected the presence of small clusters of amyloid plaques. Each cluster had high levels of iron, which the researchers said caused the MRI signal voids. Signal voids were not found in animals that were fed a normal diet.

Prashanthi Vemuri, PhD, and colleagues at the Mayo Clinic in Rochester, Minn., sought to validate the ability of a new MRI analysis algorithm known as the STructural Abnormality iNDex (STAND) score to capture Alzheimer's-related tangle severity by comparing the person's STAND-score derived from an MRI scan taken before death with the person's Braak stage calculated after death.

The researchers developed an algorithm that extracts atrophy information from an individual patient's 3D MRI scan. A STAND-score was assigned by comparing the degree of atrophy in the person's brain to atrophy patterns extracted from a large library of 160 Alzheimer's and 160 cognitively normal subjects' MRI scans.

To verify the adjusted STAND scores against Braak staging, the researchers identified 101 patients who had an MRI scan within four years of the time of death, as well as postmortem Braak staging. They compared the two and, on a scale of zero to 1, found the strength of association between the STAND-score and Braak stage to be 0.63.

According to the results, information extracted from MRI scans can accurately capture the severity of Alzheimer's tangle pathology and STAND scores may prove useful for early identification of the disease, the researchers said.

In another study reported at ICAD 2008, Christos Davatzikos, PhD, of the department of radiology at the University of Pennsylvania in Philadelphia, and colleagues examined the presence and progression of advanced high-dimensional patterns in elderly individuals who are cognitively normal, and a small group with mild cognitive impairment, from the Baltimore Longitudinal Study of Aging.

The researchers found that Alzheimer's-like patterns of brain atrophy were increasingly present in 109 healthy participants over age 80. The rate of progression of the index of Alzheimer-like patterns over time also was higher in the older participants.

Davatzikos said that the clinical significance of the patterns of brain atrophy must be further evaluated, and is hopeful that these pattern analysis tools will provide early indicators of brain changes that resemble those seen in people with Alzheimer's.