This is a prospective observational study aiming: 1) To quantify lung function using perfusion dual energy computed tomography (DECT) and use this information at the time of treatment planning with preferential sparing of functional lung parenchymal 2) to validate results of lung function obtained using DECT with lung perfusion scintigraphy results, the current standard method; 4) to compare dosimetry of whole lungs vs. functional lungs in patients treated with either stereotactic body radiotherapy (SBRT) for early stage lung cancer or conventional radiotherapy for locally advanced lung cancer and 5) to evaluate lung function 6, 12 and 24 months post-radiotherapy with both perfusion DECT and pulmonary function tests and compare radiation dose-map to functional lung-map.

Inclusion Criteria:

• ≥ 18 years
• ECOG 0-2
• Pulmonary neoplasia, confirmed histopathologically or by imaging
• Prognosis evaluated ≥ 1 year by attending MD
• Clinically acceptable lung capacity to undergo radiotherapy
• Initial assessment including history, physical examination, biochemistry, PFT, chest radiograph, chest and abdominal-pelvic scan, PET
• Written consent
• The patient must be available for treatment and monitoring. Patients registered in the study should be treated in our center.

Exclusion criteria

• Previous radiotherapy in the radiation field
• Presence of any major medical condition that, in the opinion of the investigator, would prevent follow-up at 6, 12 and 24 months post-radiotherapy.
• Iodine allergy
• Pregnancy and lactation

Patients with lung cancer planned for curative intent radiotherapy (conventional or stereotactic)