Optimization of a FLASH Proton Beam Using a Track-Repeating Algorithm
Q Wang1*, U Titt2, R Mohan3, F Guan4, P Yepes5, (1) Rice University, Houston, TX, (2) MD Anderson Cancer Center, Houston, TX, (3) UT MD Anderson Cancer Center, Houston, TX, (4) The University of Texas, MD Anderson Cancer Center, Houston, TX, (5) Rice University, Houston, TX
Presentations
PO-GePV-M-236 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: We optimize characteristics of a 86.4 MeV proton beam for FLASH experiments using the Fast Dose Calculator (FDC), a track-repeating Monte Carlo algorithm.
Methods: A phase space file located at 383 mm upstream of the isocenter is generated through tuning parameters to match FDC results with measured integrated dose distribution in water and MCNPX simulated lateral dose files in air. To spread out the Bragg Peak, widen the beam and reduce the penumbra, we insert a Ridge Filter, a high-density material Scatterer and a Collimator in the beam path and optimize their shapes, sizes and positions. The FDC calculations are validated by comparing Geant4 simulations. In addition, an algorithm to automatically choose the optimal dimension and position of the beam shaping elements is developed and tested using the same beam.
Results: The optimized beam had a 10.5 mm SOBP (from 80% to 80% of the maximum dose), 13.5 and 12.5 mm lateral width with dose above 80% and 90% respectively and a 2.5 mm penumbra from 80% to 20% in the lateral profile. The FDC calculations had passing rates above 99% using 3mm/3% as gamma-index criterion comparing with Geant4 simulations. The automatic algorithm can choose the proper radius of high-density Scatterer within 20 minutes.
Conclusion: The 86.4 MeV FLASH proton beam can be optimized by inserting proper high-density material Scatterer, Ridge Filter and Collimator. The track-repeating Monte Carlo algorithm FDC can accurately predict dose distribution when beam shaping elements are included. The automatic algorithm works efficiently in choosing dimensions for high-density Scatterer.
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