Differential background clearance of fluorodeoxyglucose activity in normal tissues and its clinical significance

The clearance of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) activity in normal tissues varies significantly with extended distribution time. Although most tissues have lower standardized uptake value (SUV) on 2-hour/3-hour delayed images, others may have stable or higher FDG activity with longer distribution times. The continuously decreased SUV on delayed imaging in some tissues, especially in the liver, indicates that longer distribution time will decrease background activity, increase lesion-to-background ratio, and thus improve imaging quality, whereas the continuously increased SUV from 1 to 3 hours in the heart suggest that longer distribution time will improve detection of viable myocardium in a viability study.