PET Effective for Diagnosing Alzheimer's

A new study confirms that positron emission tomography (PET) can be an effective diagnostic tool for identifying Alzheimer's disease. The study, conducted by researchers from Duke University Medical Center, the U.S. National Institutes of Health, and Johns Hopkins University, was reported in the November issue of The Journal of Nuclear Medicine.

The study involved 22 patients for whom standard clinical criteria yielded difficult-to-characterize memory loss or dementia. These patients were evaluated by neurologists using standardized clinical and pathologic criteria to determine their type of dementia. Using the radiopharmaceutical fluorodeoxyglucose (FDG), PET images of the brain were obtained and were graded in a blind review by a nuclear medicine doctor according to the degree of the abnormality found. All patients were tracked over time, and pathologic confirmation of the diagnosis was obtained by biopsy and/or autopsy, traditionally considered the only way to absolutely confirm the presence of Alzheimer's.

Earlier PET studies had indicated a characteristic Alzheimer's signature of metabolic abnormality (bilateral temporoparietal hypometabolism). In the current study, patients with a form of dementia other than Alzheimer's disease had FDG PET results showing abnormalities (hypometabolism) that were quite different from the pattern shown in Alzheimer's disease. The study results indicated that the PET imaging technique was sufficiently accurate to make it acceptable as a confirmatory test of Alzheimer's, particularly when used in conjunction with careful clinical evaluation and to distinguish Alzheimer's disease from other causes of memory loss.

With the advent of new medications, the possibility of stemming or delaying cognitive deterioration in Alzheimer's patients has improved. Because these therapies are most effective in mild-to-moderate cases, early diagnosis is critically important and may help prevent irreversible neurodegeneration.