Functional Lung Imaging With DECT and 4DCT

Inclusion criteria: * Patients have histologic diagnosis of non-small cell lung cancer * Patients have AJCC stage II, III or IV disease were the plan is to receive definitive concurrent chemoradiation to 60 Gy or higher * Age \> 18 years of age * Patients are able to provide informed consent * No additional lung radiation is planned until after the 2nd CT on this study (i.e. patient does not have a solitary pulmonary nodule or second primary that the plan is to undergo SBRT) * Patient must have adequate kidney function to receive IV contrast (following institutional policy supplied by radiology). The cutoff level for serum creatinine is 1.6 mg/dL * Negative urine pregnancy test before every CT scan Exclusion criteria: * Allergy to IV iodine contrast * Severe claustrophobia * Further thoracic radiation therapy is planned.