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Automatic Phase Space Generation for Monte Carlo Calculations of Intensity Modulated Particle Therapy

Q Wang1*, C Zhu2 , X Bai3 , D Yu4 , N Schlegel5 , A Adair6 , Z Chen7 , M Moyers8 , P Yepes9 , (1) Rice University, Houston, TX, (2) UT MD Anderson Cancer Center, Houston, TX, (3) University of Houston, Houston, ,(4) Shanghai Proton and heavy ion center, Shanghai, ,(5) Shanghai Proton and heavy ion center, Shanghai, ,(6) Rice University & University of Texas MD Anderson, Houston, TX, (7) Shanghai Proton and heavy ion center, Shanghai, ,(8) Shanghai Proton and Heavy Ion Center, Colton, CA, (9) Rice University, Houston, TX


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: One of the most important inputs for any Monte Carlo (MC) simulation of particle therapy are phase space files for different energies. The phase space files include information about the initial kinetic energies, positions and travelling directions of particles. The accuracy of this information plays a critical role in the performance in dose calculation. Determining parameters for phase space file is usually time consuming. The purpose of this project is to develop an algorithm to automatically and efficiently determine such parameters.

Methods: The kinematic properties of a sample of 1M particles at a plane perpendicular to the beam and centered around the beam line are used to describe a beamlet directed to the isocenter. Features of the beam are defined by a real energy (Er) and FWHM of the energy distribution (Δₑ). In addition, position and cosine of scattering angle projected in x and y axes of the plane distributions are described with some functions centered in 0 and with different FWHMs.For tuning Er and Δₑ, we compare FDC simulations with PDD measurements. While for the rest parameters, we compare lateral dose calculations with measurements in air at 5 different depths.

Results: The gamma-index passing rates for the PDD comparison are 100.0% with 0.2%/0.2 mm as a criterion for energy 48.1, 104.5 , 150.1 , 182.9 and 221.1 MeV. The average deviations of the FWHMs of lateral dose simulation from measurements are 7.9%, 4.7%, 2.5%, 4.3% and 7.7% for the 5 energies respectively.It takes about 30 minutes for the whole process per energy on server with Intel(R) Xeon(R) CPU E5-2630 v4 @ 2.20GHz with 40 cores.

Conclusion: The high gamma-index passing rates for PDD comparison and low deviations of FWHMs of lateral dose simulations from measurements validate our automatic procedure for phase space file parameters determination.


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