Detecting Radiation-Induced Cardiac Toxicity After Non-Small Cell Lung Cancer Radiotherapy

The investigators propose a longitudinal imaging pilot study composed of 20 Stage I-III NSCLC patients before, and six weeks after standard radiotherapy using a hybrid 3T-PET/MRI system (Biograph mMR, Siemens Healthcare) and a GE Revolution 256-slice CT scanner. The imaging protocol is designed to detect acute changes in myocardial perfusion, inflammation, edema, left ventricular ejection fraction, normal lung and tumour perfusion, and tumour metabolism. During each imaging session, patients will receive an 18F-FDG PET scan to image macrophage-related inflammation and tumour metabolism, MRI to identify edema, mature fibrosis or scar, and Dynamic contrast enhanced CT (DCE-CT) imaging to image perfusion and (LVEF). All images will be fused and rendered with radiation treatment planning dose distributions. Parameters such as Standard Uptake Value (SUV) will be used to compare PET scans, while heart volume and presence of Gadolinium enhancement will be used to compare MRI scans. Blood flow, blood volume, and permeability will be used to compare CT scans. Blood tests including Erythrocyte Sedimentation Rate (ESR), high sensitivity C-reactive protein, and troponin at each timepoint will also be performed to detect cardiac inflammation. Comparisons between Stage I/II and Stage III patients will allow us to determine whether our metrics for heart changes is radiation related. Relative differences from the six-week time point to baseline will be correlated with the radiation dose distribution to attempt to define a dose-response relationship between radiation dose and cardiac toxicity.