Author ORCID Identifier
Doctor of Philosophy
Dr. John S. Wilson
Purpose: To assess the cardiopulmonary-induced dose variation on the left ventricle (LV) and evaluate the spatiotemporal evolution of cardiac/aortic function following radiotherapy (RT).
Methods: 8 lung cancer patients who were scheduled to receive RT were recruited for this study. Each patient underwent one 4D-CT at baseline. MRI scans including cine GRE, T1/T2, LGE, and 4D-flow were acquired at baseline, 3-months and 6-months post-RT to evaluate the cardiac/aortic function. Finally, image registration was used to assess the cardiopulmonary-induced dose variation on the LV.
Results: Mean RT-dose was minimum during inspiration and systole (at expiration). No significant differences were found in the maximum dose during cardiac/respiratory motion. Finally, higher mean segmental cumulative doses were estimated at regions closer to the tumor location.
In regards to RT-induced cardiac/aortic toxicity, global metrics did not show any significant changes post-RT except for T2/LGE. Though, regional metrics showed significant changes over at least one follow-up with a dose-dependency response among radiobiological metrics. A correlation was observed between T1 and T2 signal, and between aortic dose and radial/circumferential strain drop at basal anteroseptal of the LV at 6-months post-RT completion.
Conclusion: To minimize the LV RT-dose, it is recommended to deliver the radiation during inspiration and systole. Radiobiological metrics precede mechanical changes in evaluation of RT-induced toxicity with a dose-dependency response over higher doses (>50 Gy). Myocardial fibrosis may induce edema or vice versa given the T1/T2 signal correlation at 6-months. Finally, aortic dose may indirectly damage LV function where LV and aorta are in mechanical continuity.
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Date of Submission
Available for download on Thursday, August 10, 2023