Date Approved

8-2-2024

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Allied Health Sciences

First Advisor

George Arnould

Academic Year

2023/2024

Abstract

Abstract

Introduction

When cancer spreads from its place of origin to a new location, it is termed ‘metastatic’. Metastatic cancer is often not curable, however palliative care can be given. One common method of palliation is in the form of radiation therapy. A common site of metastasis is in the thoracic spine, which has several nearby organs that can make treatment planning difficult. These treatments often consist of three-dimensional conformal radiotherapy methods. The purpose of this study was to compare the traditional 3DCRT techniques to a hybrid dynamic conformal arc technique. HDCAT has been used in previous studies, however none of those were palliative thoracic spine cases.

Methods

For this retrospective study, 10 patients were selected randomly from the Cancer Imaging Archive who had received a Computed Tomography (CT) scan of the chest, abdomen, and pelvis. Those that did not include the entirety of the lung and kidneys were excluded. Each patient had three different plans created; AP_PA, Wedged Pair, and HDCAT. The HDCAT plans included a dynamic conformal arc rotating from 181 degrees to 179 degrees with static fields at 0 and 180 degrees. These plans were compared by evaluating several different dose metrics and doses to Organs at Risk (OARs).

Results

When evaluating the doses to the surrounding OARs, it was found that there were a couple organs that received lower dose with the AP_PA plan. The AP_PA plans achieved a lower mean kidney dose and a lower V500 lung dose. The HDCAT and wedged pair plans had significantly lower mean heart dose and V2000 lung dose. When comparing the HDCAT and wedged pair plans, there was no significant difference in OAR dose.

Conclusion

This study suggested that the use of HDCAT over AP_PA techniques can improve the high dose to nearby OARs, but potentially increase the low dose in the process. The study was limited by a small sample size that may not be representative of all the patients who receive palliative thoracic spine radiation. Although there were several metrics that showed significant statistical difference between the plans, there was no way to correlate that to clinical significance using this study. Future studies should investigate this HDCAT technique at a larger scale and compare its usefulness in different treatment sites.

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