[Evaluation of pulmonary lesions with positron emission tomography]

Positron emission tomography (PET) with fluor-18-labeled deoxyglucose (FDG) enables metabolically oriented imaging of intrapulmonary lesions. PET is currently not used for the detection of lung metastases, but for further diagnostic differentiation of nodules that have already been detected. The diagnostic accuracy of FDG-PET is currently dependent on the size of the metastatic lesions and the uptake intensity. Significantly increased FDG uptake is strongly suggestive of malignant disease whatever the size of lesion concerned. Differentiation of a solitary metastasis from a primary lung tumor is not possible. Slightly elevated FDG uptake can also be found in tuberculosis, sarcoidosis and other granulomatous or inflammatory processes. Exclusion of metastatic disease with PET is currently only reliably possible for lesions larger than 2.0 cm in diameter, owing to respiratory motion and effects of partial volume.