BACKGROUND The uptake of 18F-FDG in brown adipose tissue (BAT) may have important implications in understanding the pathophysiology of BAT and obesity. Because of the thermal implications of BAT uptake of 18F-FDG, this study aimed to contribute to existing knowledge by assessing patients scanned in a subtropical environment with particular reference to ethnicity.
PATIENTS AND METHODS A retrospective study was carried out to determine the prevalence and pattern of BAT uptake in patients undergoing 18F-FDG PET-CT imaging in a PET facility located in a subtropical climatic zone. Standardized uptake values were obtained for regions of BAT uptake of 18F-FDG, and the distribution pattern was assessed according to anatomical region, sex, age, BMI and ethnicity.
RESULTS Following a reveiw of a total of 386 scans, 38 patients showed BAT uptake of 18F-FDG (9.85%), with the mass and activity of BAT being greater in women than in men (11.95 and 6.88%, respectively). BAT uptake of 18F-FDG in the neck/supraclavicular, axillary and mediastinal regions was greater in adults whose BMI was less than 18kg/m2. However, perirenal BAT activity was shown to be greater in obese individuals. The frequency of BAT uptake of 18F-FDG was 55% in winter as against 45% during summer (P<0.012). There was no statistical difference in BAT uptake between black and white patients.
CONCLUSION This study shows the pattern and prevalence of BAT in patients in a subtropical environment. Although the average seasonal temperatures are higher in a subtropical climate, a seasonal variation in BAT expression was observed, although there were no differences with respect to patient ethnicity.