Date Approved

8-4-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Lee Culp

Second Advisor

Kristen Vu

Academic Year

2024/2025

Abstract

Prostate cancer is among the most treated malignancies with radiation therapy, where precise dose delivery is critical for tumor control and minimizing toxicity. VMAT is widely adopted due to its efficiency and conformity; however, the choice between coplanar and non-coplanar beam arrangements remains an area of ongoing investigation, especially with newer platforms like Halcyon and TrueBeam. This retrospective dosimetric study compares coplanar and non-coplanar volumetric modulated arc therapy (VMAT) treatment plans for intact prostate cancer patients using the Varian Halcyon and Varian TrueBeam systems. Plans were created using a standardized protocol within Eclipse v16.1, with all Halcyon plans employing coplanar arcs and all TrueBeam replans incorporating at least one non-coplanar arc. The primary aim was to evaluate differences in dose coverage to the planning target volume (PTV) and dose sparing of organs at risk (OARs). Metrics such as D95, D98, conformity index, and OAR-specific dose constraints were compared using paired statistical analyses. Preliminary findings indicate that non-coplanar plans on the TrueBeam system achieved comparable or slightly improved dosimetric outcomes in select OARs while maintaining target coverage. These results suggest potential clinical benefits of non-coplanar planning in prostate radiotherapy; however, practical limitations, including complexity, feasibility of couch rotation, and treatment time, must be considered. Further investigation is warranted to assess long-term clinical outcomes.

Download

Share

COinS