Date Approved

7-30-2026

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

School of Interdisciplinary Health

First Advisor

Jessica Johnson

Second Advisor

Kristen Vu

Academic Year

2025/2026

Abstract

Medical dosimetry is constantly evolving as new techniques emerge to improve plan quality. The Eclipse treatment planning system (TPS) is equipped with the entrance and exit dose avoidance tool commonly used to prevent beam interaction with implanted metals or steer the beam away from anatomical regions. Current literature shows this tool has not been thoroughly investigated for more fundamental applications such as routine organ at risk (OAR) sparing. Xerostomia remains a lasting side effect for head-and-neck cancer (HNC) patients after the salivary glands receive substantial radiation. This study takes a more detailed look at the tool’s effectiveness when applied to a parotid gland directly adjacent to a target in head-and-neck cases. Thirteen patients with high-, intermediate-, and low-risk target volumes were replanned using the most current methods of simultaneous integrated boost (SIB) technique with 6 megavoltage (MV) flattening-filter-free (FFF) energy. Two plans were generated for each patient: one without avoidance and one with entrance avoidance applied to the parotid gland contralateral to the high-risk target. Target coverage, OAR constraints, and overall plan quality were analyzed. All three targets achieved acceptable coverage regardless of technique.  The low-risk target, located adjacent to the parotid gland blocked in one leg of the study, showed negligible differences when compared to the plan that did not apply any avoidance. These findings provide direction for Eclipse users to implement in their practice.

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