Ventilation Using Radiographic Examination: Functional Lung Imaging Techniques for the Reduction of Toxicity in Functional Avoidance Radiation Therapy

The goal of this observational validation study is to determine the best implementation of fluoroscopic and CT ventilation imaging in patients having non-stereotactic ablative body radiotherapy (non-SABR) radiotherapy for stages II-IV lung cancer. The main questions it aims to answer are: * Assess the dosimetric variation in functional avoidance radiation therapy (RT) plans produced using these ventilation imaging techniques, * Establish a quality assurance procedure for functional lung avoidance radiation therapy, and * Evaluate the clinical acceptable thresholds for accuracy of the method. Participants will: Prior to radiation therapy treatment, patients will undergo: 1. A standard of care 4DCT scan for radiation therapy simulation, 2. Pulmonary Function Tests (PFT) 3. A 4D attenuation correction CT 4. Breath Hold Computed Tomography (BHCT) imaging where static end-inspiration and end-expiration BHCT scans will be acquired, 5. Nuclear medicine imaging where a Tc-99m MAA SPECT perfusion scan and a Galligas PET ventilation scan will be acquired, 6. Fluoroscopy where 1-breath cine-fluoroscope sequences will be acquired at five different angles across the chest, 7. A 4D Cone Beam Computed Tomography (4DCBCT) scan. 8. Scans in points 4 to 7 above will be repeated at the end of treatment. Individual participants provide their own internal control. Galligas PET ventilation images (control) are compared with ventilation images derived from additional scans (comparator) for each participant. Tc-99m MAA SPECT perfusion images (control) are compared with perfusion images derived from BHCT scans (comparator) for each patient. There will be no change to patient treatment and patients will be treated using a standard of care anatomical based treatment plan. The pre-treatment 4DCBCT scan is part of standard of care.