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PET scans show promise in detecting beta amyloid deposition in Alzheimer's disease

Thursday, November 20 2008 | Comments

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What's This? By Kate Kahn

A new study provides further evidence that positron emission tomography (PET) imaging using the radiotracer Pittsburgh Compound B (PiB) may allow assessment of beta-amyloid deposition in the brains of patients with Alzheimer's disease.

While it has been previously demonstrated that PiB has a high affinity for amyloid binding in postmortem studies, it has not been clear how well PiB binding levels reflect the antemortem clinical features during the course of Alzheimer's disease.

The findings of the current study suggest that PET imaging using PiB may be a valid method for detecting beta amyloid (A beta) plaques in early Alzheimer's disease and in monitoring anti-A beta therapies.

In this autopsy study, Dr. Milos Ikonomovic from the departments of neurology and psychiatry at the University of Pittsburgh and colleagues analyzed tissue homogenates of the superior frontal cortex from 36 patients. The subjects had antemortem clinical diagnoses of Alzheimer's disease (n=14), mild cognitive impairment (n=12), or no cognitive impairment (n=10). In vitro [3H]PiB binding and A beta ELISA assays were performed on the tissue homogenates.

Subjects with Alzheimer's disease had significantly greater frequencies of neuritic and diffuse A beta plaques (P=.0017 and P=.0083, respectively) in the superior frontal cortex when compared to those with no cognitive impairment. However, there was no difference in the frequencies of neuritic and diffuse A beta plaques between the Alzheimer's disease patients and those with mild cognitive impairment.

In addition, the Alzheimer's disease subjects had significantly greater levels of [3H]PiB binding and total A beta peptides in the superior frontal cortex compared to the group with no cognitive impairment (P<.01). There was no significant difference between the Alzheimer's disease group and the group with mild cognitive impairment. While researchers found a direct correlation between [3H]PiB binding with neuritic plaques, diffuse plaques, and regional A beta peptide levels, they found no correlation with neurofibrillary tangles.

The authors concluded that there is a clear association between PiB and plaque pathology. In addition, the researchers observed an increase in PiB binding and A beta peptide levels in patients with poorer cognitive performance. These findings lend further validity to the use of PiB-PET imaging in the evaluation of A beta pathology and therapies targeting A beta deposition in the treatment of Alzheimer's disease. (Program 47.5, Poster V25)

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