Date Approved

8-16-2022

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Health Professions

First Advisor

Destiny Jacobs

Academic Year

2021/2022

Abstract

Introduction

HyperArc-VMAT and GammaKnife treatment techniques are both considered to be the best types of SRS treatment methods regarding conformity, homogeneity, gradient, and mean brain dose. The BED calculation is used to calculate the treatment regimens that are effective biologically and used for extrapolation to normal tissue limits.

Methods

This is a retrospective study that analyzes 15 lesions from 10 randomly selected patients with brain metastasis within the cerebrum. Each of the lesions had a single fraction treatment plan created using the same PTV for the HyperArc-VMAT and GammaKnife techniques. Each treatment technique was dose escalated until the healthy brain tissue constraint for a single fraction CNS radiosurgery of V12Gy < 5-l0cc was maxed out. That dose was then used for the BED calculation and two the treatments were compared.

Results

An independent sample t-test was conducted to evaluate the hypothesis that there will not be a correlation between the BED when comparing the two treatment techniques, HyperArc and GammaKnife, when evaluating the tumor size and normal brain tissue. The results indicated no statistical significance of the BED of the HyperArc and the GammaKnife treatment techniques. The HyperArc BED mean is 33177.07 (range: 2637- 137108) and the GK BED mean is 37146.53 (range: 1710- 156000). The BED shows a negative correlation when looking at the increase of tumor size.

Conclusion

GammaKnife had the highest BED, however there was no significant correlation between the two treatment techniques that were compared. In conclusion, the overall results of this study exhibit that the GK and HyperArc treatment plans had similar biological effective doses.

Available for download on Thursday, August 17, 2023

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