Date Approved

8-8-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Robert Hammond

Academic Year

2024/2025

Abstract

This retrospective planning study compared dosimetric outcomes and treatment efficiency between flattening filter free (FFF) and standard volumetric modulated arc therapy (VMAT) plans for left breast accelerated partial breast irradiation (APBI) under deep inspiration breath hold (DIBH) and free-breathing (FB) conditions. Ten patients with early stage left breast cancer were replanned to create four plans each: FFF VMAT and standard VMAT in DIBH and FB. All plans prescribed 30 Gy in 5 fractions. Measures included planning target volume (PTV) coverage, mean heart dose, ipsilateral lung V30%, contralateral breast maximum dose, and monitor units (MUs). Statistical analysis used repeated-measures ANOVA with Bonferroni correction and Cohen d effect size evaluation. All plans achieved PTV V95% >95% with no significant coverage differences. DIBH significantly reduced mean heart dose and left lung V30% compared with FB (Bonferroni corrected P< .008; large effect sizes). Differences between FFF and standard VMAT were minimal for organ-at-risk (OAR) sparing, whereas FFF plans required significantly more MUs (mean difference ~200–300; P< .001; large effect size). Contralateral breast and right lung doses were low and similar across all techniques. Breathing technique exerted the greatest impact on dosimetry, confirming the importance of DIBH for cardiac and pulmonary protection, while FFF and standard VMAT provided comparable dose distributions except for higher MUs in FFF plans, which may affect operational efficiency rather than clinical benefit.

Download

Share

COinS