Physiological uptake values of 18F-FDG in long bones of the lower extremity on PET/CT imaging.

Abstract

Fluorine-18 fluorodeoxyglucose (F-FDG) PET/computed tomography (CT) has proven to be a valuable imaging modality with high diagnostic accuracy for the detection of bone infections. However, the physiological uptake values for F-FDG in the long bones of the lower extremity have not been established yet. This hampers correct interpretation of a F-FDG-PET/CT scan. The purpose of this study was to determine the physiological uptake values of F-FDG in the long bones of the lower extremities, including the femur and the tibia. We retrospectively analyzed the F-FDG-PET/CT scan of 84 consecutive patients from our database. F-FDG uptake parameters included mean standardized uptake value (SUVmean) and maximum standardized uptake value (SUVmax). Both SUVs were determined in the diaphyseal region of the femur and the tibia. SUVmean for the femoral diaphysis was 0.46 [95% confidence interval (CI) 0.42-0.49] and SUVmax was 0.81 (95% CI 0.74-0.88). For the tibial diaphysis, SUVmean was 0.34 (95% CI 0.32-0.37) and SUVmax was 0.61 (95% CI 0.56-0.65). SUVmean and SUVmax of the femur were significantly higher than that of the tibia (both P<0.01). SUVs for men were not significantly different from that for women and did not discriminate between age classes. For a correct interpretation of the F-FDG-PET/CT scan, we have determined the F-FDG uptake values in the long bones of the femur and the tibia. A SUVmean less than 0.5 and a SUVmax less than 0.8 can be considered as normal bone, irrespective of sex or age.