Efficacy of robust optimization plan with partial-arc VMAT for photon volumetric-modulated arc therapy: A phantom...

Area of Science:

• Radiation Oncology
• Medical Physics
• Radiotherapy Planning

Background:

• Volumetric Modulated Arc Therapy (VMAT) is a radiotherapy technique.
• Robust optimization aims to minimize dose uncertainties in radiotherapy plans.
• Position dependence of treatment planning strategies requires investigation.

Purpose of the Study:

• To compare position dependence in planning target volume (PTV)-based and robust optimization plans for full-arc and partial-arc VMAT.
• To evaluate the impact of gantry angles and CTV position on dose uncertainties.

Main Methods:

• Investigated PTV-based and robust optimization plans using full-arc and partial-arc VMAT.
• Simulated isocenter shifts (1-5 mm) in A-P, S-I, and R-L directions.
• Analyzed uncertainties in CTV D99% doses at periphery, intermediate, and center positions.

Main Results:

• No significant difference in D99% dose uncertainties between PTV-based and robust plans for intermediate and center CTV positions (P > 0.05).
• Robust optimization showed significantly lower D99% dose uncertainties in the R-L direction for periphery CTV positions compared to PTV-based plans (P < 0.05).

Conclusions:

• Robust optimization plan efficacy with partial-arc VMAT is dependent on the CTV's periphery position.
• The R-L direction demonstrated improved robustness for periphery CTVs with robust optimization.