Date Approved

8-6-2026

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Corinne Dallas

Academic Year

2025/2026

Abstract

Abstract

Purpose: Dynamic conformal arc (DCA) is a three-dimensional (3D) radiation therapy technique that can be used to deliver a simultaneous integrated boost (SIB) during whole-breast irradiation (WBI). This study investigated whether the depth of the lumpectomy cavity affects the feasibility of creating a successful DCA SIB treatment plan for breast radiotherapy.

Methods and Materials: 30 patients who previously received WBI followed by a 3D sequential boost (SeqB) were selected for this retrospective study. A DCA plan was created for each patient and combined with the original whole-breast tangent fields to create a SIB plan. Each plan was required to meet the same target coverage and organ-at-risk (OAR) dose limits as the original sequential boost (SeqB) plan. Measurements including cavity depth, cavity volume, breast volume, breast laterality, and cavity location were recorded. Statistical tests were used to compare geometric measurements with plan quality and to compare dose spillage between SeqB and SIB plans.

Results: All 30 DCA SIB plans met target coverage and OAR constraints. Lumpectomy cavity depths ranged from 0.0 cm to 9.69 cm, and no limiting depth was found within this range. Maximum cavity depth was related to hotspot dose, while minimum cavity depth was related to both hotspot dose and high-dose spillage. Compared with SeqB plans, DCA SIB plans resulted in overall less high dose spillage than the SeqB plans.

Conclusions: DCA SIB planning was successful for all patients in this study. Although cavity depth affected some dose measurements, no limit on cavity depth was identified. These results suggest that DCA SIB is a practical treatment option for many breast radiotherapy patients and may reduce high-dose spillage compared with sequential boosts.

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