The overall goal of this project is to investigate the diagnostic performance of integrated F-18 fluorodeoxyglucose-positron emission tomography (FDG-PET) and Dual Energy CT (DECT) imaging in determining the thoracic nodal status of small-cell lung cancer (SCLC) and non-small-cell lung cancer (NSCLC), and its impact on target volume delineation for image guided radiation therapy (IGRT) planning.