Prospective Evaluation of Physiologic Uptake Detected with True Whole-Body 18F-FDG PET/CT in Healthy Subjects

Abstract

PET is a molecular imaging modality used to assess metabolic activity. Little is known about the physiologic uptake of radiopharmaceuticals such as (18)F-FDG in healthy subjects. This study was designed to identify and describe normal patterns of physiologic uptake of (18)F-FDG in healthy adult subjects and to examine the influence of low-level muscle activity during the (18)F-FDG uptake phase. Twenty healthy adults received an intravenous injection of (18)F-FDG and were subsequently scanned with a combined PET/CT scanner. The CT scan was used to accurately identify the location of (18)F-FDG uptake. Of the 20 subjects, 10 were randomly selected to perform a low-level muscle activity during the 1-h (18)F-FDG uptake phase. The PET/CT images were fused, and the location and intensity of metabolic activity were described for all subjects. Muscle activity during the (18)F-FDG uptake phase affected the pattern of (18)F-FDG distribution on PET scans. In addition, the tissue uptake of (18)F-FDG, although variable, showed some consistency among tissue types. The data suggested that technologists should be aware of low-level muscle activity before and during uptake to avoid potential false-positive interpretations. The data also showed that there is some variability in the normal physiologic uptake of (18)F-FDG across subjects. Finally, the results suggested that (18)F-FDG uptake may be used for the evaluation of muscle activity.