Date Approved

8-10-2025

Graduate Degree Type

Project

Degree Name

Medical Dosimetry (M.S.)

Degree Program

Allied Health Sciences

First Advisor

Emilie Soisson

Academic Year

2024/2025

Abstract

This study aimed to evaluate the dosimetric impact of Hybrid Arc Palliative Radiation Therapy (HART) versus conventional anterior-posterior/posterior-anterior (APPA) beam arrangements for thoracic spine metastases. The primary objective was to assess differences in conformity, homogeneity, and organ-at-risk (OAR) sparing between the two techniques. A retrospective plan comparison was conducted using anonymized datasets from twenty patients previously treated with HART. Each case was replanned using a standard APPA technique, normalized to match the target coverage of the original HART plan within 0.1%. All plans were prescribed 20 Gy in 5 fractions. Plan quality was evaluated using conformity index (CI), homogeneity index (HI), and predefined dose-volume metrics. Plans using the HART technique demonstrated significantly improved dose conformity (median CI 1.16 vs. 2.63, P = .0004) and homogeneity (median HI 1.12 vs. 1.25, P < .0001) compared to APPA plans. The APPA technique delivered higher doses to critical structures, including the spinal cord, esophagus, heart, stomach, and small bowel. HART increased low-dose exposure to the liver, kidneys, lungs minus clinical target volume (CTV), and small bowel, although all values remained within clinically acceptable limits. Compared to APPA, HART provided superior target conformality and homogeneity while reducing high-dose exposure to critical thoracic structures. These findings support HART as a promising approach for palliative thoracic spine radiation, with potential to improve patient comfort and reduce treatment-related toxicity.

Download

Share

COinS