Date Approved
8-8-2025
Graduate Degree Type
Project
Degree Name
Medical Dosimetry (M.S.)
Degree Program
Health Professions
First Advisor
Daniel Pham, PhD
Second Advisor
Kristen Vu, M.S.
Academic Year
2024/2025
Abstract
Purpose
Non-small cell lung cancer (NSCLC) patients benefit by starting radiation therapy (RT) promptly upon diagnosis. Diagnostic scan-based radiation therapy planning (DBRP) eliminates the need for computed tomography (CT) simulation. This is a retrospective study comparing dosimetric differences between volumetric arc therapy (VMAT) diagnostic scan-based plans recalculated onto simulation CT scans.
Methods
Radiotherapy (60 or 66 Gy in 20-30 fractions) for eight NSCLC patients was planned on diagnostic CTs. The plans were recalculated onto the fused simulation CTs, mimicking first treatment setups. Dose-volume histogram (DVH) were used to compare the minimum dose received by 95% of the planning target volume and 98% of the gross tumor volume (PTV D95%, D98%, and GTV D98%), the minimum dose received by 2% of the PTV (PTV D2%), plan homogeneity (defined as D2% divided by the prescription dose), and doses to organs at risk (lungs, heart, esophagus, spinal cord, left anterior descending artery (LAD), bronchial tree, and brachial plexus).
Results
Significant differences were observed between the differences in medians of PTV D95% [-4.8%, sign test, p-value=0.01, E.S.=1.15], PTV D98% [-8.6%, sign test, p-value=0.01, E.S.=1.13], and nodal GTVn D98% [-6.7%, sign test, p-value=0.01, E.S.=1.07]. Significant differences were observed in the median PTV D2% [+2.7%, sign test, p-value=0.01, E.S.=1.14] of the PTV volumes (PTV D2%) and the median homogeneity indexes [+3.7%, sign test, p-value=0.01, E.S.=1.03]. No significant differences were observed in the primary GTVp D98% or in the doses to organs at risk (OAR).
Conclusion
The median plan differences observed are similar to parametric results observed in dosimetry comparison studies of palliative-intent DBRP. A successful DBRP process for NSCLC patients was retrospectively demonstrated, suggesting that the technique may be feasible for some definitive RT courses. The study’s limitations were a small number of patients and a simplified target delineation process. Further research is needed to determine processes specific to NSCLC for DBRP. Special quality assurance measures and processes would also be needed.
ScholarWorks Citation
Langer, Joshua, "Diagnostic Imaging-based Radiation Therapy Planning (DBRP) for Non-Small Cell Lung Cancer (NSCLC) Patients" (2025). Culminating Experience Projects. 637.
https://scholarworks.gvsu.edu/gradprojects/637
