This study is designed to test a novel technology to examine early changes in the lung in hopes of identifying patients who may be at risk for radiation pneumonitis. Eligible subjects will undergo standard of care treatment with the use of the Varian TrueBeam system for radiation therapy of a cancer lesion in the chest. The imaging data acquired as part of usual standard of care for these patients is a pre-treatment 4D planning CT scan, and a daily cone beam CT at each radiation treatment visit. We will also obtain a series of images consisting of five six-second cinefluorographs (real time fluoroscopic movies, for a total each time of 30 seconds of fluoroscopy) of the lungs while the subject is breathing, each at precisely measured angles to the subject, on 4 different occasions. This study will compare lung function data generated by applying High Fidelity Functional Lung Imaging (HFFLI) software to 4D CT, cone beam CT, and fluoroscopic images of the lungs breathing to determine the degree of correlation between data generated from different imaging modalities. The study is open to adults over the age of 18, at any stage of cancer.