Imaging of beta-amyloid plaques in vivo with 18F-FDDNP

Objective: Alzheimer disease (AD) is the most common form of dementia. The hallmark pathological features of AD include amyloid senile plaques (APs) and neurofibrillary tangles (NFTs). This study was designed to determine the localization and load of APs and NFTs in the brains of AD patients, and to evaluate the diagnostic value of 18F-2-(1-{6-[(2-18F-fluoroethyl)(methyl) amino]-2-naphthyl} ethylidene) malononitrile (FDDNP) PET in differentiating AD from vascular dementia (VD). Methods: Nineteen subjects were divided into three groups: 7 AD patients, 6 VD patients and 6 normal control (HC) subjects. Sequential dynamic emission scans were obtained in 3 AD patients immediately after 18F-FDDNP administration. All other subjects had emission scans obtained at 5, 25 and 45 min after 18F-FDDNP administration. The PET results were analyzed by visual inspection and by ROI quantification. The ratios of radioactivity clearance defined by the ROI brain regions from 5 to 25 min and from 5 to 45 min after 18F-FDDNP administration were calculated. Results: 18F-FDDNP crossed and cleared from the blood brain barrier very rapidly. Visual and ROI methods found that AD patients typically showed marked retention of 18F-FDDNP in the related cortical regions where large amount of amyloid deposited. In VD patients, only the striatum demonstrated lower clearance of 18F-FDDNP. Conclusion: 18F-FDDNP PET imaging may be promising in providing reliable quantitative information on APs and NFTs in AD patients and in differentiating between AD and VD. (authors)