Date Approved

7-28-2024

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Biology

First Advisor

Johnso Sarah

Academic Year

2023/2024

Abstract

Abstract

Introduction:

Radiation therapy using tangential fields is a common treatment for breast cancer, targeting the tumor while reducing radiation exposure to surrounding healthy tissues such as the heart and lungs. Forward-planned "field-in-field" IMRT (FP-IMRT) is widely used for its ability to provide uniform dose distribution and spare normal tissue, despite requiring high planning skill and time. Inverse-planning IMRT (IP-IMRT) offers better conformal dose to targets with reduced planning variability and time. This study compares FP-IMRT and IP-IMRT in left-sided breast cancer patients using the deep inspiration breath hold (DIBH) technique.

Method:

A retrospective analysis was conducted on 10 patients treated with hypofractionation protocol. Each patient was planned using FP-IMRT and IP-IMRT techniques with the same beam orientation and prescription. Metrics for breast coverage and dose to organs at risk (OARs) were analyzed using IBM SPSS Statistics.

Result:

Results showed no significant difference in the dose covering 5% and 95% of the planning target volume (PTV) between FP-IMRT and IP-IMRT. However, IP-IMRT significantly reduced hot spots compared to FP-IMRT. For OARs, IP-IMRT demonstrated a lower mean lung dose, though there were no significant differences in lung V20Gy and V5Gy between the techniques. Heart dose metrics were comparable, with IP-IMRT showing a slight advantage.

Conclusion:

This study concludes that IP-IMRT provides similar breast coverage to FP-IMRT while reducing hot spots and mean lung dose, making it a preferable option for left-sided breast cancer treatment using the DIBH technique. Further research with a larger patient cohort is recommended to validate these findings.

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