Dynamic Changes of FDG Uptake and Clearance in Normal Tissues

This study aims to evaluate dynamic 2-deoxy-2-[F-18]fluoro-d-glucose (FDG) uptake in normal tissues. Thirty male patients underwent FDG positron emission tomography (PET)/computed tomography imaging at 1, 2, and 3 h after tracer injection. Standardized uptake values (SUV) were obtained in regions of interest of normal tissues. The aorta (blood pool), liver, and spleen FDG activity demonstrated significantly and continuously decreased activity from 1 to 2 and 2 to 3 h, while FDG uptake in the lungs, pancreas, lymph nodes, and skeletal muscle decreased from 1 to 2 h only. In contrast, the left ventricular myocardium demonstrated two patterns of dynamic changes: myocardium with higher FDG uptake (SUVmax a parts per thousand yenaEuro parts per thousand 3.25) on the initial images had more remarkable increased activity on the delayed images, while myocardium with lower FDG uptake (SUVmax < 3.25) on the initial imaging had no increased uptake on delayed imaging. Increased FDG uptake was also observed in the bones on the delayed images. No significant changes of FDG uptake were noted in the parotid gland, thyroid gland, and prostate gland. These findings may help nuclear medicine physicians when comparing images performed at different time points, when using FDG uptake in internal reference regions as a relative indicator of FDG uptake in a specific lesion, and when reading a delayed FDG PET imaging.