Integrated F-18 fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) system represents a powerful imaging tool widely and effectively utilized in oncology allowing functional and anatomical information to be acquired in a single examination session. Proper interpretation of FDG PET/CT images requires knowledge of the normal physiologic distribution of the tracer, frequently encountered physiologic variants, and benign pathologic causes of FDG uptake that can be confused with a malignant lesion.
We report three cases, in which focal intrapulmonary FDG uptake would have been interpreted as false positive malignant tumor mass in the lung if no anatomic correlation would have been performed. All patients were studied by 18F-FDG PET performed according to the standard procedure (6 h of fasting, intravenous injection of 370 Mbq of 18F-FDG and image acquisition with a PET/CT scanner for 4 min per bed position).
Focal high uptake of 18F-FDG observed in lung lesions without anatomical counterparts on CT, possibly represent a iatrogenic microembolism. As two patients of three presented a paravenous injection, the lung microembolisms probably originated at the injection site. Furthermore no corresponding radiologic abnormalities were found in CT studies repeated within the following month after the primary PET/CT scannings.
Combined PET/CT interpretation of hot-clot artifacts in FDG PET/CT imaging has an important contribution on avoiding an erroneous staging and a following mistreatment in oncological patients.