Date Approved
8-3-2026
Graduate Degree Type
Project
Degree Name
Medical Dosimetry (M.S.)
Degree Program
School of Interdisciplinary Health
First Advisor
George Arnould
Academic Year
2025/2026
Abstract
Purpose
To evaluate the dosimetric impact of interfraction anatomical changes in patients with head and neck cancer and assess whether observed dose variations support adaptive radiotherapy decision-making within the framework of the B-ART trigger.
Methods and Materials:
A retrospective dosimetric analysis was performed on 15 patients with base of tongue and/or hypopharyngeal squamous cell carcinoma treated with curative-intent volumetric-modulated arc therapy using a simultaneous integrated boost technique. All patients underwent daily cone-beam computed tomography (CBCT) image guidance. The CBCT acquired on the final day of treatment was rigidly registered to the planning CT, and the clinically delivered treatment plan was transferred without modification. Dose was recalculated using the original monitor units to evaluate anatomical and dosimetric variation throughout treatment. Dosimetric parameters for planning target volumes (PTVs) and organs at risk (OARs) were compared between initial and final plans. Statistical analysis included Shapiro–Wilk testing, paired t-tests, and Wilcoxon signed-rank tests, with significance defined as P < 0.05.
Results:
Statistically significant differences were observed in multiple target coverage metrics, including PTV1 D95% and D98%, PTV2 D98%, V95%, and V100%, and PTV3 D98%, V95%, and V100% (P < 0.05). Significant changes were also identified in PTV volume measurements.
Among OARs, oral cavity mean dose demonstrated a significant reduction in the final plans compared with the initial plans (P = 0.0225), with a small-to-moderate effect size. Significant differences were also observed in left and right parotid gland volumes, while left parotid mean dose approached statistical significance (P = 0.0574). No significant differences were observed for spinal cord, brainstem, or body maximum dose metrics.
Conclusions:
CBCT-based dose recalculation demonstrated that anatomical changes occurring during head and neck radiotherapy can result in significant alterations in target coverage and selected OAR dose parameters. While critical maximum dose constraints remained largely stable, the observed variations in PTV coverage and oral cavity dose suggest that certain patients may benefit from adaptive evaluation during treatment. These findings support continued investigation of trigger-based adaptive radiotherapy approaches, including the B-ART framework, to identify patients at risk for clinically meaningful dosimetric deviation.
ScholarWorks Citation
Reeves, Jeremiah, "Evaluating the B-ART Trigger as a Predictor of Dosimetric Deviation Requiring Replanning in Curative-Intent Head and Neck Radiotherapy Patients" (2026). Masters Projects. 735.
https://scholarworks.gvsu.edu/gradprojects/735
