RecruitingDrug trialHyperpolarized Xenon-129 Magnetic Resonance Imaging in Lung Cancer Patients Receiving Radiation Therapy for Investigating Radiation-response and ToxicityThe goal of this clinical research study is to learn if novel type of imaging scan called HP 129Xe MRI can help doctors identify and predict common side effects of radiation therapy. Rather than contrast-enhanced MRIs, the tracer (129Xe) will be inhaled rather than injected. The 129Xe tracer has not been FDA approved. Its use in this study is investigational.