[PET/CT: focal lung uptake of 18F-fluorodeoxyglucose on PET but no structural alterations on CT]

The combination of positron emission tomography (PET) and computed tomography (CT) in a single device (PET/CT) offers a powerful diagnostic tool that opens up new horizons for imaging diagnosis. In order to correctly interpret PET/CT studies, knowledge of the biodistribution of 18F-fluorodeoxyglucose (FDG), the physiological variants as well as the pitfalls, including artefacts, which may be found, is necessary. We report four cases performed during the follow-up diagnostic context of an oncology study performed with 18F-FDG-PET/CT. In every case, this study showed focal uptake in the lung parenchyma in the PET study with no structural lesions being found on the CT scan. Radiotracer extravasation in three of these patients and a recent change in the injection protocol used suggest that an artefact was responsible for these discrepancies.