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Validation the Robustness of Breast Intensity-Modulated Proton Plans Against Setup Errors

X Liang1*, D Zheng2, R Mailhot Vega, Z Li, N Mendenhall, J Bradley, (1) Department of Radiation Oncology, University of Florida College of Medicine, Jacksonville, FL (2) University of Nebraska Medical Center, Omaha, NE

Presentations

(Sunday, 7/12/2020)   [Eastern Time (GMT-4)]

Room: AAPM ePoster Library

Purpose: validate the robustness of breast intensity-modulated proton plans against clinical setup errors

Methods: patients who went through breast IMPT treatment in our institute were consecutively selected for this study. Treatment planning was conducted on the RayStation TPS with dose prescription of 50 GyRBE in 25 fractions. For each plan, 2 en-face beam angles were used and the plan unitized single-field optimization. Plan was robust optimized on CTV with 5 mm setup uncertainty and 3.5% range uncertainty. Both the optimization and dose computation used a Monte Carlo algorithm. The plans were normalized so that 92-95% of the target volume received 95% of the prescription dose according to the treating physician’s discretion. All patients had a verification CT halfway through the treatment to evaluate the setup reproducibility and dosimetry consequence. The verification CT was rigid registered to the planning CT by aligning the bony structures, using the same method used for daily setup. Thereafter, the verification dose was computed. The target coverage on CTV was evaluated.

Results: the verification plans were able to meet our institutional acceptable criteria of V90 = 90% and D90 = 90%.The Mean (SD) of the CTV coverage drop was 0.13(0.17)Gy on D90, 0.29(0.28)Gy on D90, 1.02(0.82)Gy on D99, 0.51%(0.44%) on V90 and, 1.16%(1.61%) on V95.

Conclusion: robustness our robust optimized IMPT breast plans was validated and approved to be able to provide acceptable target coverage under setup error scenarios.

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Keywords

Protons, Breast, Patient Positioning

Taxonomy

Not Applicable / None Entered.

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