FDG-PET Imaging Allows Early Detection of Alzheimer's, Other Dementia Types

Caroline Cassels

April 03, 2008

April 3, 2008 — New research shows positron emission tomography (PET) in combination with the radiotracer flurodeoxyglucose (FDG) can accurately detect and classify different types of dementia in up to 94% of cases — a finding that investigators say could lead to better dementia treatment and possibly even prevention.

In a large multicenter study that included 7 centers in the United States and Europe, investigators at the New York University (NYU) School of Medicine used optimized FDG-PET analysis techniques to measure glucose metabolism in different regions of the brain and successfully distinguish patients with mild cognitive impairment (MCI), Alzheimer's disease (AD), dementia with Lewy bodies (DLB), and frontotemporal dementia (FTD).

"We used FDG-PET to measure how efficiently the brain utilizes glucose and observed distinct regional patterns of hypometabolism in patients with different types of dementia," the study's first author, Lisa Mosconi, PhD, told Medscape Neurology & Neurosurgery.

The study is published in the March issue of the Journal of Nuclear Medicine.

Diagnosis Ahead of Treatment

In the largest FDG-PET study to measure brain metabolism in different dementing disorders to date, investigators compared the cerebral metabolic rate of glucose in the cortex and hippocampus of 110 normal healthy elderly subjects and 114 MCI, 199 AD, 98 FTD, and 27 DLB patients.

Building on previous research from 2005, in which Dr. Mosconi and colleagues developed a technique that allowed accurate imaging of the hippocampus for the first time, the current study showed that the hippocampus metabolizes glucose less efficiently as AD progresses.

"The hippocampus is probably the most important brain region for memory function and the first brain structure to be affected by pathological lesions in AD. Therefore, it should be the first one we focus on for the early detection of Alzheimer's and to aid in differential diagnoses," she said.

Dr. Mosconi added that the optimized FDG-PET technique, which was developed in collaboration with senior study author Mony de Leon, EdD, also from NYU, was able to distinguish between mild and moderate to severe disease in all dementia types.

Best Hope

At this point, diagnosis of dementia is ahead of therapy, in that there are no Food and Drug Administration–approved agents for the treatment of mild or preclinical disease. Furthermore, the agents that are available address dementia symptoms rather than the underlying pathology.

Nevertheless, said Dr. Mosconi, as new treatments become available, early detection of dementia through FDG-PET could facilitate early intervention and aid in assessing the efficacy of various agents in different types of dementia.

Furthermore, she said, preclinical diagnosis could potentially allow physicians to intervene at a very early stage and address known dementia risk factors such as hypertension, hypercholesterolemia, elevated blood glucose levels, and diabetes in an effort to prevent or delay dementia progression.

"Our best hope is to be able to identify people as soon as possible and not wait until they are symptomatic, because by then it is really too late. So many studies have shown that once patients have clinical symptoms there is a limit to what can be done. Whereas identifying patients when the brain is still functioning normally offers a great advantage from a therapeutic point of view," said Dr. Mosconi.

The team is currently analyzing 2-year follow-up data to determine how accurate optimized FDG-PET is in predicting patients' clinical outcomes.

The study was supported by the National Institutes of Health, the Alzheimer's Association, and the European Union.

J Nucl Med. 2008;49:390-398. Abstract


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