Date Approved

4-21-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Allied Health Sciences

First Advisor

Bethany Marshall

Second Advisor

Kristen Vu

Academic Year

2024/2025

Abstract

Introduction: The pancreas is surrounded by several critical organs, making it challenging to treat with external beam radiation therapy (EBRT). Previous studies have shown that applying biological constraints, such as the generalized equivalent uniform dose (gEUD), to organs at risk (OARs) can effectively reduce the radiation dose to these structures. This study evaluated whether adding a target gEUD constraint to the planning target volume (PTV) would improve target coverage in patients with pancreatic cancer.

Methods: Three separate treatment plans were created for ten randomly selected pancreatic cancer patients. The first plan applied only physical (dose-volume) constraints to the PTV while using a combination of physical and biological (gEUD) constraints for the OARs. This first plan was then duplicated to generate two additional plans: one incorporating a target gEUD constraint with an alpha value of -10, and the other with an alpha value of -20.

Results: No statistically significant differences were observed in the maximum dose, minimum dose, or the percent volume of the PTV receiving 95% of the prescription dose (V95%) across the three plans. Similarly, the maximum and mean doses to the OARs did not differ significantly between the plans.

Conclusion: Adding a gEUD constraint to the PTV did not improve target coverage or significantly affect doses to the OARs. However, plans with a target gEUD showed a slight increase in maximum dose and a slight decrease in minimum dose to the PTV. Future research should include a larger sample size and investigate different anatomical sites and a wider range of alpha values to better assess the potential benefits of incorporating target gEUD constraints.

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