Date Approved
8-6-2025
Graduate Degree Type
Project
Degree Name
Medical Dosimetry (M.S.)
Degree Program
Allied Health Sciences
First Advisor
Sarah Johnson
Second Advisor
Kristen Vu
Academic Year
2024/2025
Abstract
Background: In inverse treatment planning, the timing of applying organ-at-risk (OAR) constraints during the optimization process can influence dosimetric outcomes. This study investigates the effects of introducing OAR constraints at different stages of the multi-resolution optimization process within the Eclipse Treatment Planning System (TPS).
Purpose: To determine the optimal resolution level for applying OAR constraints that achieves the best dosimetric balance between target coverage and normal tissue sparing.
Methods: Thirteen prostate cancer treatment plans were generated using an anonymized pelvic CT dataset from The Cancer Imaging Archive. All plans were developed in GVSU Virtual Eclipse TPS using the Photon Optimizer and Acuros XB dose calculation algorithm. Clinical target volume (CTV) and planning target volume (PTV) objectives were consistently applied at Multi-Resolution Level 1, Step 1. OAR constraints for the bladder, rectum, penile bulb, and femoral heads were introduced at varying optimization steps across four planning scenarios. Dosimetric outcomes were assessed using metrics from the RTOG 0938 protocol. Statistical analysis was conducted with a significance threshold of p < 0.003.
Results: Statistically significant differences in dosimetric outcomes were observed based on when OAR constraints were introduced. Plans with OAR constraints applied at run 3 (Level 1, Step 3) yielded the most consistent improvements across target coverage and OAR sparing. Run 1 (Level 1, Step 1) also demonstrated competitive results, particularly in rectum and femoral head sparing. The greatest bladder sparing was observed in run 5 (Level 1, Step 5).
Conclusions: The timing of OAR constraint application in Eclipse’s multi-resolution optimization process significantly affects dosimetric quality. Applying constraints at resolution Level 1, Step 3 offers the most favorable trade-off between target coverage and OAR sparing. These findings support the use of adaptive optimization strategies based on resolution level to improve radiotherapy treatment planning.
ScholarWorks Citation
Jeon, Ji Hyun, "Dosimetric Comparison of Organ-at-Risk Constraints Across Multi-Resolution Levels in Eclipse Planning Optimization" (2025). Culminating Experience Projects. 642.
https://scholarworks.gvsu.edu/gradprojects/642
