Alteration of normal regional brain FDG uptake in normal aging

Objectives: Normal aging alters the brain structure and function, which can be detected using modern in vivo functional imaging modalities such as ¹⁸F-FDG PET. It is highly important to recognize normal age-dependant changes in order to correctly diagnose pathologic states. The goal of current study is to evaluate the age-related changes in regional brain FDG uptake in normal healthy population.

Methods: This study is part of the Cardiovascular Molecular Calcification Assessed by ¹⁸F-NaF PET/CT (CAMONA) study. CAMONA was approved by the Danish National Committee on Health Research Ethics registered at ClinicalTrials.gov (NCT01724749). 40 normal healthy subjects were prospectively recruited in group A (22-32 years) and B (56-66 years) and underwent 18F-FDG PET/CT. Static images were obtained 180 minutes following ¹⁸F-FDG injection. Supratentorial (including individual measurements for frontal, parietal, occipital and temporal lobes) and cerebellar FDG uptakes were measured by manual placement of ROIs (regions of interest) over these regions based on predefined criteria for each and SUV mean values were calculated using OsiriX software.

Results: The mean ages of the patients in group A was 26.1±3.4 versus 62±3.9 for group B. There were 10 females (50%) in group A and 12 females in group B (60%, p=0.37). Mean SUV of cerebellum was 6.84±1.25 for the young subjects compared to 6.04±0.99 among old subjects (independent t-test, p=0.03). Mean SUV of supratentorial brain was 9.34±2.37 for the young subjects compared to 7.20±0.98 among old subjects (p<0.001). When the measurements were done for frontal, and temporal lobes as well as parietooccipital region, higher uptake was seen in all three areas among young patients (Table 1). More interestingly, Mean SUV of supratentorial brain was significantly higher among female healthy volunteers in both groups (p= 0.040 and 0.034, respectively).

Conclusion: In conclusion, these findings confirm age dependent reduction of supratentorial 18F-FDG uptake among healthy individuals, slightly more accentuated in the frontal region. Table 1: Comparison of SUV_meanin different brain regions. Data is presented as Mean±SD.