Date Approved

7-28-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Addah Riebschleger

Second Advisor

Kristen Vu

Academic Year

2024/2025

Abstract

This study evaluated and compared the dosimetric outcomes and treatment efficiency of three radiation therapy techniques, Hybrid volumetric arc therapy (H-VMAT), Modified volumetric arc therapy (M-VMAT), and traditional Three-Arc volumetric arc therapy (T-VMAT), in the treatment of lower-third esophageal cancer. Ten patients with esophageal cancer located in the lower third of the esophagus were retrospectively replanned using each technique. H-VMAT combined 3-dimensional anterior-posterior/posterior-anterior (AP/PA) fields with two partial VMAT arcs. The M-VMAT technique included two full arcs and one arc with avoidance sectors. The T-VMAT technique used three full arcs. Each plan was prescribed 5040 cGy in 28 fractions using 6 MV photons. The dose constraints evaluated included lung V5, lung V20, mean heart dose, heart V40, spinal cord maximum dose, integral lung dose, maximum dose, monitor units, and estimated treatment time. Statistical analysis was performed using repeated-measures ANOVA, and Bonferroni-adjusted post hoc tests were employed to assess statistical significance. It was found that H-VMAT significantly reduced the dose to the lungs compared to M-VMAT and T-VMAT, but resulted in significantly higher doses to the heart and spinal cord. H-VMAT required fewer monitor units (MUs) and had the shortest treatment time. Additionally, M-VMAT provided a favorable balance between dose conformity, sparing of organs at risk (OAR), and delivery efficiency. These findings support the selection of individualized techniques based on patient anatomy and clinical priorities.

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