Use of Dual Energy Computed Tomography in Thoracic Radiotherapy Planning.

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.