El Cuerpo Académico de Partículas Campos y Relatividad General invita cordialmente a su próximo seminario
A. Ramos Méndez
Este seminario se llevará a cabo en la
Sala de Conferencias 111B/302
Miércoles 21 de marzo de 2012
Purpose: To implement a geometrical particle splitting technique in order to reduce the computation time in the production of phase space files in Monte Carlo calculations in proton therapy and to validate the dose profiles generated from these phase spaces with respect to reference simulations.
Method and Materials: The gantry mounted treatment nozzle at the Northeast Proton Therapy Center at Massachusetts General Hospital was modeled with a new Monte Carlo simulation tool. Two particle-splitting planes were implemented, one immediately downstream of the second ionization chamber the other immediately upstream of the aperture of the treatment nozzle and phase spaces in IAEA format were recovered for five different geometries set up. The symmetry of the proton beam was considered to split the particles in a factor of 4 per plane at different locations rotated around the z-axis; particles different than protons were killed immediately after produced and all particles were stopped at phase space by timing considerations. The computational efficiency was calculated for each phase space and comparisons between dose profiles were recovered for a voxelized water phantom for both, the reference and optimized simulations. Dose calculation in realistic patient also was simulated to compare the performance of the technique.
Results: Normalized computational efficiency between 10 and 14.5 were reached for the several configurations. Percentage difference between dose profiles in a water tank of the simulations done with and without particle splitting is within the statistical precision of 2%. Dose distribution in realistic patient shows differences up to 4% in the regions of interest. Conclusions: By considering the cylindrically symmetric region of the nozzle and the splitting planes separated at strategic distance, considerable time reduction can be recovered while the precision is keeping unbiased. Difference in the dose at patient can be reduced with more statistics.