Date Approved

8-6-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Sarah Johnson

Second Advisor

Kristen Vu

Third Advisor

Raj Mitra

Academic Year

2024/2025

Abstract

This study compares the dosimetric performance and fit accuracy of ClearSight and Superflab boluses in head and neck (HN) volumetric modulated arc therapy (VMAT) treatment plans, focusing on dose distribution and air gap volumes. A RANDO anthropomorphic phantom was used to simulate HN VMAT treatment for oral cavity cancer with positive lymph nodes, prescribed 70 Gy in 35 fractions. Four configurations were tested: ClearSight bolus over a thermoplastic mask (CSO), ClearSight under a mask (CSU), Superflab over a mask (SFO), and Superflab under a mask (SFU). Five computed tomography (CT) scans, one without bolus and four with bolus, were performed and air gaps were contoured. Dose delivery was measured using thermoluminescent dosimeters (TLDs) at five locations, calculating the ratio of planned to delivered dose. The Kruskal-Wallis test and Dwass, Steel, Critchlow-Fligner method assessed differences in dose ratios. Mean dose ratios ranged from 1.02 (CSU) to 1.15 (CSO), with standard deviations from 0.03 (CSU) to 0.13 (SFO). The Kruskal-Wallis test (P=0.1261) showed no significant differences in dose ratios among configurations. Pairwise comparisons confirmed no significant differences (P-values: 0.1250–0.9893). Air gaps were smaller for Superflab (55.64 cm³ SFO, 17.07 cm³ SFU) than ClearSight (70.60 cm³ CSO, 30.04 cm³ CSU), indicating better Superflab fit. Air gaps were smaller when bolus was placed under a mask. No statistical analysis was possible for air gaps due to single measurements. ClearSight and Superflab boluses provide comparable dose distribution in HN VMAT, with no significant differences in dose accuracy. Superflab exhibits better fit due to smaller air gaps, but ClearSight’s transparency may aid setup. Small sample size and single metric analysis limit conclusions. Further studies with larger cohorts and repeated measurements are needed to confirm findings and assess clinical implications.

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