Foot skin depots of 18F-fluorodeoxyglucose do not enable PET/CT lymphography of the lower extremity lymphatic system in man

BACKGROUND In mice, 18F-fluorodeoxyglucose (18F-FDG) positron-emission tomography/computed tomography (PET/CT) lymphography enables detailed imaging of the lymphatic system and quantification of lymph node function. If this applies to humans, it may improve staging of several malignancies. The aim of this study was to elucidate whether foot skin depots of 18F-FDG make PET/CT imaging of the lower extremity lymphatic system possible in man. FINDINGS In four healthy volunteers, 18F-FDG depots (5 MBq in 0.1-mL isotonic saline) were injected intradermally in one foot and subcutaneously in the other. Activity was measured in blood samples drawn simultaneously from the great saphenous veins about 5 cm proximal to the ankle joints and a medial cubital vein before and every minute for 15 min after depot injection. Immediately thereafter, a low-dose CT was performed from the ankles to the pelvis followed by two consecutive PET scans of the same region.Blood activity increased faster and to a greater extent in the great saphenous veins compared to the medial cubital vein. PET/CT images showed activity in the superficial and deep veins of the lower extremities. No lymphatic collectors or nodes were visualized. CONCLUSION Neither subcutaneous nor intradermal injection of 18F-FDG allows imaging of the lower extremity lymphatic system in man.