The purpose of this study is to look for low levels of oxygen (hypoxia) in lung cancer using a positron emission tomography (PET) scan. Hypoxia can influence how lung cancer grows and responds to treatments like radiotherapy and chemotherapy. The use of PET scans to measure hypoxia may be better and simpler than the approaches used previously. This study will assess whether or not PET scans can provide useful information about hypoxia in lung cancer.