El Cuerpo
Académico de Partículas Campos y Relatividad General invita
cordialmente a su próximo seminario
José
A. Ramos Méndez
FCFM, BUAP
Este
seminario se llevará a cabo en la
Sala de Conferencias 111B/302
Miércoles 21 de marzo de 2012
12:00 hrs.
Resumen:
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.