The influence of adipose tissue volume can significantly affect the metabolic activity of reference organs in 18F-FDG PET/CT studies of a normal healthy population.

OBJECTIVE This study investigated whether fluorine-18-fluorodeoxyglucose (18F-FDG) uptake of reference organs can be affected by subjects' factors in positron emission tomography/computed tomography (PET/CT) in a healthy population. SUBJECTS AND METHODS A total of 208 normal healthy subjects without diabetes or dyslipidemia were included. Adipose tissue volume was measured by CT images from a dedicated PET/CT scan. Uptake of 18F-FDG of reference organs was measured from liver, blood pool, and muscle, and was normalized by lean body anthropometric data and adipose tissue volume. RESULTS Of 208 participants, 118 were metabolically healthy lean (MHL); with body mass index (BMI) <25kg/m2 and 90 were metabolically healthy obese (MHO) with; BMI≥25kg/m2 . These subjects had significantly higher values of liver, blood pool, and muscle than did the MHL subjects (P<0.001 for both). Among subjects' factors, adipose tissue volume revealed strongest correlation with standardized uptake value multiplied by lean body weight divided by body weight (SUL) of liver (r=0.754, P<0.001), of blood pool (r=0.756, P<0.001) and of muscle (r=0.635, P<0.001). On regression analysis, adipose tissue volume was determined to be a common independent predictor for SUL of liver, blood pool and muscle (P<0.001) and furthermore was serum C-reactive protein level for SUL of the liver and also age and serum insulin level for SUL of blood pool. CONCLUSION Adipose tissue volume can significantly affect SUL of liver, blood pool, and muscle in a healthy population. Liver and blood pool may have limited roles as reference organs for normalization of 18F-FDG uptake of the lesion.