According to this study:

* One type of positron emission tomography, FDDNP-PET, may be useful for detecting Alzheimer disease in its early stages.

* It may also be useful in tracking the course of the disease.

It may be possible to detect the initial development of Alzheimer disease and to noninvasively track its progress using positron emission tomography (PET).

Research has identified two proteins, &b.beta;-amyloid and tau, that accumulate in identifiable patterns in different regions of the brain as mild cognitive impairment progresses to Alzheimer disease. But such patterns are generally discernible only on autopsy or, sometimes, through biopsy. So researchers injected an "amyloid-binding radiotracer" into volunteers with self-reported memory impairment in an attempt to determine whether the subjects had Alzheimer disease, mild cognitive impairment, or no symptoms of the disorder.

The study involved 83 out of 108 recruited patients, ages 49 to 84 years. The volunteers had all undergone neurologic and psychiatric evaluation and PET. Twenty-five were found to have Alzheimer disease, 28 had mild cognitive impairment, and 30 had normal cognitive functioning.

All participants were injected with FDDNP, a fluorescing molecule that binds to senile plaques and neurofibrillary tangles in vitro, and underwent PET. In addition, all subjects underwent a different type (FDG) of PET, and 72 underwent magnetic resonance imaging. Compared with the control group, researchers found FDDNP-PET global binding to be the most diagnostically accurate measure.

In a two-year follow-up involving a subgroup of patients, greater increases in FDDNP binding were found among subjects who had clinical evidence of disease progression, thereby demonstrating for the first time the ability to accurately track the progression of Alzheimer disease. -CP