Positron emission tomography (PET) is emerging as a powerful tool that complements conventional radiologic assessment (chest radiographs, CT scans, MR imaging) of thoracic abnormalities. PET is a physiologic imaging technique that uses radiopharmaceuticals produced by labeling metabolic markers such as amino acids or glucose with the positron-emitting radionuclides fluorine-18, carbon-11, or oxygen-15. The radiopharmaceutical is typically imaged by coincidence detection of the two 511-KeV photons that are produced by annihilation of the emitted positrons.

In the thorax, PET has been used to evaluate cardiac abnormalities, including myocardial viability, but most research has focused on its application in tumor imaging. The radiopharmaceutical, ¹⁸F-2-deoxy-D-glucose (FDG), a D-glucose analog labeled with fluorine-18, is ideally suited for tumor imaging. PET performed with this agent exploits the differences in glucose metabolism between normal and neoplastic cells. After intravenous administration, FDG preferentially accumulates within neoplastic cells, allowing accurate, noninvasive differentiation of benign versus malignant abnormalities by PET imaging. This article focuses on the current applications of FDG-PET in the thorax and reviews the evaluation of focal pulmonary opacities, lung cancer staging, tumor recurrence, treatment response, and prognosis.