Quantitative Assessment of Cardiac Functional Response after External Beam Radiotherapy using Non-invasive Multi-Modality Imaging

External beam radiation treatment is often included in standard breast cancer and non-small cell lung cancer patients’ curative management. With the advances in radiation treatment (RT) techniques, such as the development of intensity-modulated radiation therapy and volumetric modulated arc therapy, local and regional control benefits are established. However, both cancer type survivors are prone to develop radiation-induced cardiac disease in their cured life. Furthermore, our laboratory previously demonstrated an inflammatory response in canine models using 18FDG/PET imaging during the initial year following RT. Hence, the overall goal of this thesis is to assess early functional changes and inflammation response in the heart after irradiation in both animal and patient pilot studies with the use of multi-modality imaging. Additionally, planning studies were undertaken to investigate the potential of reducing dose to the heart and substructure, including the left ventricle and the left anterior descending artery, which are unintentionally subjected to a higher dose during RT. Various RT planning techniques including deep-inspiration breath-hold and 4D Robust optimization, which can be applied to treat breast cancer are also examined. This is aimed to provide clinically feasible alternative options for patients who are non-compliant to breath-hold, without compromising target coverage. In this thesis, we established a clinically feasible protocol to assess early cardiac functional changes and inflammation response of current radiation treatment techniques that are dedicated to minimizing cardiac dose and radiation-induced cardiac toxicity. This included multi-modality cardiac imaging assessment using hybrid PET/MR and CT perfusion imaging with serial blood work performed. Additionally, from the extensive dosimetric heart sparing treatment planning study, we were able to demonstrate/present clinical feasible free-breathing options for patients who are non-compliant with breath-hold treatment. In the future, the benefits of cardiac dose mitigation strategies can be evaluated with the use of multi-modality imaging techniques