Date Approved

8-8-2022

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Sarah Johnson MS, CMD, R.T.(T)

Academic Year

2021/2022

Abstract

Introduction: The purpose of the study is intended to determine if gEUD optimization can be useful in the treatment planning for SBRT to the spine. The main goal was to study the dose effects when placing gEUD objectives on the targeted vertebral structure (Target gEUD) and spinal cord (Upper gEUD). Furthermore, to provide a better understanding of the utility of this tool.

Methods: Two planning techniques for SBRT spine treatments were compared retrospectively on 10 radiation therapy patients. The Varian Eclipse treatment planning system was utilized with the volumetric modulated arc therapy treatment technique. The planning techniques used different objectives in the optimizer. One plan used dose volume (DV) objectives on both the Spinal cord and target. The other plan used a combination of DV and generalized uniform equivalent objectives (gEUD) on both spinal cord and target. Plans were evaluated using dose volume histograms and statistical analysis of each plan.

Results: Based on the comparative analysis between the two planning techniques it was found that the specific use of the target gEUD in this setting did not improve the plan quality. The target gEUD constraint in the optimizer while providing a homogenous dose to the target increased the maximum dose beyond what would be clinically acceptable. Both plans were able to spare the spinal cord effectively.

Conclusion: For the treatment of the spine in the SBRT setting the sparing of the cord is of utmost importance and both planning techniques managed this well. The use of the target gEUD in the SBRT setting did not provide a benefit when looking at the overall plan quality. Recommendations to the use of the target gEUD should be further investigated.

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