Author Type

Graduate Student

Date of Award

Fall 11-16-2025

Document Type

Thesis

Publication Status

Version of Record

Submission Date

November 2025

Department

Physics

Degree Name

Professional Science Masters (PSM)

Thesis/Dissertation Advisor [Chair]

Andreas Kyriacou

Abstract

For free-breathing volumetric modulated arc therapy (VMAT), a major challenge in dose delivery is accounting for planning target volume (PTV) motion from respiration. To minimize PTV underdosing, this study implemented a 1.5 cm virtual bolus (VB) to create skin flash. A brass mesh bolus was also modeled in the treatment planning system to simulate its clinical impact. Different Hounsfield Units (HU) were assigned to the VB to determine the most effective value.

Five post-mastectomy breast cancer patients treated with VMAT were retrospectively analyzed. Plan normalization values, conformity indexes, and dosimetric criteria were compared to find the optimal HU for the VB. The plan using the -500 HU VB to create skin flash required the least adjustment in plan normalization to meet clinical standards. This planning-based study supports the use of a -500 HU VB to create skin flash when incorporating a brass mesh bolus during VMAT treatment.

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