Date Approved

8-16-2023

Graduate Degree Type

Project

Degree Name

<-- Please Select One -->

Degree Program

Health Professions

First Advisor

Daniel Pham

Academic Year

2022/2023

Abstract

Abstract

Introduction

The study investigated the consistency of free breathing planning margins for fractionated SBRT treatment in the lung. The study compared breathing motion from the average CT (AVE CT) scan to the Cone Beam Computed Tomography (CBCT) from each treatment session. Various breathing techniques were also discussed, including deep inspiration breath hold (DIBH), gated breathing, abdominal compression (AC), and free breathing (FB). Free-breathing may lead to overdosing on surrounding healthy tissue if significant changes in breathing amplitude occur. Abdominal compression or breath hold may reduce abnormal breathing movement if erratic breathing occurs. The study's aim was to ensure the accuracy of radiation therapy by accurately matching the patient's position to the AVE CT.

Methods

The study collected retrospective cohort data to analyze the consistency of free breathing planning margins for SBRT lung treatment. The study included ten patients diagnosed with malignant neoplasm of the lung and compared breathing motion from the AVE CT scan to the CBCT from each treatment session. The study emphasized the importance of careful monitoring during treatment to ensure the accuracy of radiation therapy. The study's data comparison may reveal a correlation between diaphragm-PTV distance and tumor motion during breathing. A paired sample test assesses the significance of diaphragm movement and PTV-diaphragm distance. Distribution and probability plots identify any anomalies that correlate to the tumor motion.

Results

The study found that careful monitoring during treatment is essential to ensure accurate treatment. The paired sample test showed no significant difference in diaphragm movement between CBCT and AVE CT. The PTV-diaphragm distance showed a correlation with tumor motion during breathing. The study identified an outlier, subject 10, significantly impacting the correlation between PTV-diaphragm and tumor motion. Overall, the study emphasizes the importance of monitoring and adjusting for accurate radiation therapy.

Conclusion

SBRT patients undergoing treatment with a PTV margin of ITV + 5mm received minimal impact on the surrounding healthy tissue. Patients with irregular breathing patterns significantly changed the average of their diaphragm distance during CBCT, which can impact the treatment. Deep or shallow breathing can also significantly affect the treatment of the patient. The closer the target is to the diaphragm, the more pertinent the proper repetition of normal breaths becomes. Overall, the study emphasizes the importance of careful monitoring and adjustment during treatment to ensure the accuracy of radiation therapy.

Keywords

sbrt, interfractional, intrafractional, average ct, sign test, signed rank test, diaphragm movement, ptv to diaphragm, tumor motion, lung sbrt, half arc, vmat, imrt, malignant neoplasm

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