Analysis of cerebral beta amyloid deposition with increasing age in cognitively normal adults using Florbetaben PET

Objectives: Florbetaben (FBB) PET is a useful diagnostic tool for the diagnosis of Alzheimer's disease, but there is little research on the quantitative value of normal group data of the test. The purpose of this study was to investigate the relationship between increased age and cerebral amyloid deposition in the normal group using FBB PET. Methods Thirty adults with normal cognitive ability underwent intravenous injection of 8 mCi of FBB and the PET images were acquired after 90 minutes. Each ten subjects were recruited for each age group of 50s (male: female = 8: 2, mean age = 55.7 ± 2.6 years), 60s (male: female = 1: 9, mean age = 63.9 ± 2.7 years) and 70s (male: female = 6: 4, mean age = 74.3 ± 2.8). For quantitative analysis, the region-of-interest (ROI) was defined and the SUV ratio (SUVR) was calculated for the frontal lobe, anterior cingulate gyrus, temporal lobe, parietal lobe, occipital lobe, posterior cingulate gyrus using Syngo.via (Siemens). Cerebellar cortex was used as a reference region. Brain region values of all subjects were analyzed by the Robust method to obtain the upper limit of reference thresholds. The tendency of amyloid deposition changes with increasing age among three independent groups was analyzed by Kruskal-Wallis and Jonckheere-Terpstra trend test (p < 0.05). Results Neuropsychological tests were implemented to evaluate cognitive function of participants. In all participants, the range of education year was 5-16, MMSE score was 26-30, CDR-GS was 0-0.5, CDR-SB was 0-2. The PET images were read by two qualified experts and all determined as negative by visual analysis. Using Kruskal-Wallis test, SUVR of each brain regions shows no significant difference in the amyloid burden between the three groups ( frontal lobe; p = 0.87, anterior cingulate gyrus; p = 0.21, temporal lobe; p = 0.74, parietal lobe; p = 0.37, occipital lobe; p = 0.14, posterior cingulate gyrus; p = 0.93). The threshold values by the Robust method were 1.41 for frontal lobe, 1.18 for anterior cingulate gyrus, 1.68 for temporal lobe, 1.28 for parietal lobe, 1.34 for occipital lobe, 1.56 for posterior cingulate gyrus, and 1.35 for mean SUVR. Conclusions The results show that amyloid deposition does not show a difference with increasing age in cognitively normal subjects. In other words, no significant effect of age on cerebral amyloid deposition was found in this study. Moreover, another result, the upper threshold determined in the normal group, can be an index that serves to select the target group requiring surveillance for Alzheimer's dementia.

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