Equal sensitivity of early and late scans after injection of FDG for the detection of Alzheimer pattern: an analysis of 3D PET data from J-ADNI, a multi-center study.

OBJECTIVE

To determine the optimal accumulation time for three-dimensional positron emission tomography (3D-PET) with (18)F-2-fluoro-2-deoxy-D-glucose ((18)F-FDG) to detect the brain uptake pattern typical of Alzheimer's disease (AD).

METHODS

Patients with mild AD or amnestic mild cognitive impairment (MCI) and normal control subjects were recruited in the Japanese Alzheimer's disease neuroimaging initiative and examined with a PET scan during the 30-60 min after FDG injection. Three independent blinded experts interpreted the 30- to 60-min sum images, and images of patients with AD and MCI presenting AD patterns and normal subjects presenting normal patterns were used in the analysis. Early-scan (ES) and late-scan (LS) images were obtained from the data acquired at 30-35 min and 55-60 min after the injection, respectively. Separate target regions of interest (ROI) for ES and LS were defined as areas of significant reductions in the posterior cingulate and parietotemporal lobe in both hemispheres from the results of an initial cohort with 21 patients (AD 16, MCI 5) and 19 controls. A subsequent sample of 36 (AD 9, MCI 27) patients and 38 controls were used to compare the diagnostic capability of ES and LS using Z scores within the target ROI in individual statistical parametric mapping analysis.

RESULTS

Compared to LS, ES showed lower activity in the frontal lobes and higher activity in the venous sinus than LS; however, the diagnostic capability of ES and LS did not significantly differ (sensitivity 0.97 and 0.97, specificity 0.82 and 0.84, area under the receiver-operating characteristic curve 0.96 and 0.97, respectively).

CONCLUSIONS

For a qualitative diagnosis of the AD pattern in 3D FDG-PET, results of ES were equivalent to those of LS. ES may be an option to shorten the entire PET procedure time, particularly in diagnosing early stages of AD.