Date Approved


Graduate Degree Type


Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Destiny Jacobs

Academic Year





Breast cancer is a prevalent malignancy among women in the United States, necessitating a variety of treatment strategies. Accelerated Partial Breast Irradiation (aPBI) has emerged as an effective treatment technique for early-stage breast cancer, offering reduced treatment duration and potential benefits in terms of cosmesis and patient convenience. One of the critical factors influencing the success of APBI is the choice of beam arrangement during radiation delivery. This research paper presents a dosimetric comparison of coplanar and non-coplanar beam arrangements for APBI treatment techniques.


The study includes 15 patients with left-sided breast cancer. The patients underwent two treatment plans each, one using coplanar volumetric modulated arc therapy (coVMAT) and the other incorporating non-coplanar volumetric modulated arc therapy (ncVMAT). Dosimetric parameters, including target coverage, homogeneity, gradient index, conformity index, and dose to critical structures such as the heart, lungs, and contralateral breast, were evaluated and compared between the two techniques. Dose constraints were based on the Florence Trial phase III study.


Results revealed that the addition of a non-coplanar field in ncVMAT led to a reduced maximum dose to the ipsilateral lung, potentially minimizing lung complications. The heart dose was also lower with ncVMAT, although the significance was borderline. The contralateral breast dose met constraints for both techniques. Dosimetric indexes, including Homogeneity Index (HI), Conformity Index (CI), and Gradient Index (GI), showed no significant differences between the two treatment methods.


The study highlights the importance of limiting dose to the OARs in APBI treatment. Despite some advantages of ncVMAT, including lower lung and heart doses, implementation challenges such as treatment efficiency and collision risk should be considered. The small patient sample size limits the generalization of the findings, warranting further research with larger patient populations and exploring different treatment techniques. APBI treatment using VMAT, whether coplanar or non-coplanar, shows promise for early-stage breast cancer patients. The findings indicate that non-coplanar plans offer advantages in terms of normal tissue sparing, highlighting their potential for enhancing treatment outcomes and minimizing radiation-related toxicities. Larger studies are needed to validate the dosimetric benefits of non-coplanar techniques and their clinical implications.