Date Approved


Graduate Degree Type


Degree Name

Medical Dosimetry (M.S.)

Degree Program

Allied Health Sciences

First Advisor

Daniel Pham, PhD, CMD, RT (T)

Academic Year



Radiation therapy has significantly improved breast cancer survival rates; however, it can still lead to long-term side effects, particularly affecting the heart. Left-side breast cancer patients face higher risks due to the proximity of the heart to the treatment area. To mitigate cardiac toxicity, various strategies, including jaw tracking and Volumetric Modulated Arc Therapy (VMAT), have been proposed. This study investigates the dosimetric impact of VMAT plans with and without jaw tracking on the left anterior descending artery (LAD) dose and heart mean dose in post-mastectomy breast cancer patients. Ten patients previously treated with VMAT were evaluated, and the results were analyzed using paired samples t-test. The study found that the presence of jaw tracking did not have a significant effect on the LAD or heart dose. Although there was a reduction in LAD dose for 70% of patients with jaw tracking, the clinical relevance of the 100cGy difference requires further investigation. Considering the lack of statistical significance and potential trade-offs in other critical structures, the study suggests that patients need not seek treatment at a different location solely due to the absence of jaw tracking on a specific machine. Further research and clinical studies are necessary to comprehend the clinical implications of small dose differences on critical structures in breast cancer radiotherapy planning. The data analysis did not yield a significant t-value, indicating that the choice of a specific machine for treatment should not unduly inconvenience the patient. Balancing lower lung dose versus LAD dose is crucial due to the numerous variables and critical structures involved. Although jaw-tracking plans exhibited lower average maximum and mean doses, the difference was not statistically significant compared to plans without jaw-tracking. In conclusion, while the use of jaw tracking should be considered if available, this research indicates that it may not be the sole determining factor for plan quality.