Dynamics of fluorine-18-fluorodeoxyglucose uptake in the liver and its correlation with hepatic fat content and BMI

PURPOSE: The aim of this study was to explore the rate of elimination of fluorine-18-fluorodeoxyglucose (F-FDG) from the liver and assess the impact of hepatic fat and obesity on F-FDG clearance in early and delayed PET scans. We hypothesized that an increase in liver fat may cause a decline in hepatic F-FDG elimination with potential consequences as measured by dual time-point F-FDG PET/CT imaging. PATIENTS AND METHODS: A total of 32 patients from the Cardiovascular Molecular Calcification Assessed by F-NaF PET/CT (CAMONA) clinical trial (17 males, 15 females; mean age: 47.2 years, range: 23-69 years, mean BMI: 27.2 kg/m) were enrolled and underwent F-FDG PET/CT 90 and 180 min after tracer injection. Global mean standardized uptake value (SUVmean) (i.e. the average of SUVmean in segmented liver slices) and average maximum standardized uptake value (SUVmax) (i.e. the average of the SUVmax values recorded in same slices) were calculated for semiquantification of liver F-FDG uptake at both time-points. Percentage difference in global SUVmean and average SUVmax were also calculated to yield respective retention indices (RImean and RImax). Changes in global SUVmean, average SUVmax, RImean, and RImax from 90 to 180 min were correlated with BMI and liver fat content as measured by CT Hounsfield units. RESULTS: There was a 12.2±3.5 percent reduction in global liver SUVmean and a 4.1±5.8 percent reduction in average SUVmax at 180 min scan as compared with the 90 min time-point. RImean and RImax were inversely correlated with liver fat content and positively correlated with BMI. CONCLUSION: We observed a time-dependent decrease in global hepatic SUVmean and average SUVmax, which was affected by the amount of liver fat. Patients with higher BMI and hepatic fat content tended to retain F-FDG.