Fluorodeoxyglucose uptake in absence of CT abnormality on PET-CT: What is it?

Figure 2 Iatrogenic uptake in the lung. A 35-year-old woman with history of low grade serous ovarian cancer had fluorodeoxyglucose positron emission tomography-computer tomography (PET-CT) for initial staging. Axial PET image of the lungs shows a focus of intense uptake in the left lower lobe (arrow), but no nodule or lesion is seen on CT. Subsequent diagnostic CT was negative as well for lung nodule. The uptake is likely secondary to microembolism due to a paravenous injection.