[PET-CT for evaluation of the solitary pulmonary nodule: an update]

Positron emission tomography (PET) with 18F-FDG has become an important tool for the characterization of solitary pulmonary nodules (SPN).

The results of the main meta-analyses show that the sensitivity and specificity of 18F-FDG PET for determining malignancy of SPN are close to 95% and 80% respectively. The limits of the technology are now well known. False negative results are mainly due to certain histological types with low metabolic activity (such as bronchiolo-alveolar carcinoma and typical carcinoid), or small size (nodules less than 8 mm). False positives are mainly represented by granulomatous and infectious processes.

A gain in accuracy occurred with the advent of hybrid PET/CT machines that combine the functional data from 18FDG-PET and the morphological data of computed tomography. Improved imaging protocols (eg. injection of iodinated contrast media) could further enhance the performance of PET-CT. Further improvements will rely on respiratory synchronization protocols and on the advent of new PET tracers.

18F-FDG PET-CT should be performed for any nodule over 8 mm in size when the pre-test probability of malignancy is not deemed negligible.