Normal patterns of regional brain 18 F-FDG uptake in normal aging.

OBJECTIVE: Normal aging alters the brain function even in the absence of recognizable structural changes, which can be detected using modern in vivo functional imaging modalities such as fluorine-18 fluorodeoxyglucose positron emission tomography (18 F-FDG PET) scan. It is highly important to recognize normal age-dependent changes in order to correctly diagnose pathologic states. The goal of the current study was to evaluate the age-related changes in regional brain 18 F-FDG uptake in normal healthy population.

SUBJECTS AND METHODS: This study was part of the cardiovascular molecular calcification assessed by 18 F-sodium fluoride (NaF) (CAMONA) PET/computed tomography (CT) study. This study was approved by the Danish National Committee on Health Research Ethics registered at ClinicalTrials.gov (NCT01724749). Forty normal healthy subjects were prospectively recruited in group A (22-32 years) and B (56-75 years) and underwent 18 F-FDG PET/CT. Static images were obtained 180 minutes following 18 F-FDG injection. Supratentorial (including individual measurements for frontal, parieto-occipital and temporal lobes) and cerebellar 18 F-FDG uptakes were measured by manual placement of region of interest (ROI) over these regions based on predefined criteria for each and standardized uptake value (SUVmean) values were calculated using OsiriX software.

RESULTS: The mean ages of the patients in group A was 26.1±3.4 versus 61±4.4 for group B. There were 10 females in group A and 10 females in group B. Mean SUV of cerebellum was 6.80±1.21 for the young subjects compared to 6.08±0.7 among old subjects (independent t-test, P=0.028). Mean SUV of supratentorial brain was 9.14±1.83 for the young subjects compared to 6.92±072 among old subjects (P<0.001). Mean SUV of frontal (9.72±1.97 vs. 7.03±0.69), temporal (7.37±1.52 vs. 5.65±0.68) and parieto-occipital region (10.7±2.28 vs. 7.41±0.79) was higher among young patients (P<0.001). More interestingly, SUVmean of supratentorial brain was significantly higher among female healthy volunteers in both groups (P= 0.025 and 0.047 for group A and B, respectively).

CONCLUSION: In conclusion, these findings confirm a significant age dependent reduction of supratentorial 18 F-FDG uptake among healthy individuals. However, cerebellum 18 F-FDG uptake reduction was not so redundant. Fluorine-18-FDG uptake of all cerebral lobes including frontal, parieto-occipital and temporal decreases with normal aging in a same fashion. Interestingly, among both young and old female subjects, higher uptake was seen in supratentorial brain.