A particle track-repeating algorithm for proton beam dose calculation

Abstract

A particle track-repeating algorithm has been developed for proton beam dose calculation for radiotherapy. Monoenergetic protons with 250 MeV kinetic energy were simulated in an infinite water phantom using the GEANT3 Monte Carlo code. The changes in location, angle and energy for every transport step and the energy deposition along the track were recorded for the primary protons and all secondary particles. When calculating dose for a patient with a realistic proton beam, the pre-generated particle tracks were repeated in the patient geometry consisting of air, soft tissue and bone. The medium and density for each dose scoring voxel in the patient geometry were derived from patient CT data. The starting point, at which a proton track was repeated, was determined according to the incident proton energy. Thus, any protons with kinetic energy less than 250 MeV can be simulated. Based on the direction of the incident proton, the tracks were first rotated and for the subsequent steps, the scattering angles were simply repeated for air and soft tissue but adjusted properly based on the scattering power for bone. The particle step lengths were adjusted based on the density for air and soft tissue and also on the stopping powers for bone while keeping the energy deposition unchanged in each step. The difference in nuclear interactions and secondary particle generation between water and these materials was ignored. The algorithm has been validated by comparing the dose distributions in uniform water and layered heterogeneous phantoms with those calculated using the GEANT3 code for 120, 150, 180 and 250 MeV proton beams. The differences between them were within 2%. The new algorithm was about 13 times faster than the GEANT3 Monte Carlo code for a uniform phantom geometry and over 700 times faster for a heterogeneous phantom geometry.

Benchmark measurements and simulations of dose perturbations due to metallic spheres in proton beams

“…The track repeating algorithm proposed by Li et al (2005) and Yepes et al (2009a) predicts dose distributions using two conceptually distinct steps, first the pre-computation of proton trajectories or “tracks” in a homogeneous water phantom using a Monte Carlo code. Then, for the geometry under investigation, the proton tracks are reused or “repeated”, where the pre-computed tracks are adjusted to take into account any differences in the materials relative to the materials used to generate the pre-computed tracks.…”

Simulation and optimization of sludge hygienization research irradiator

“…The path taken by the pathogen in the irradiator determines the amount of dose rate that it will be exposed to. There are broadly two ways to evaluate the dose absorption [13,17,9]: (i) Eulerian approach by simulation of an additional transport equation, and (ii) Lagrangian approach by particle tracking in the post-processing phase. In the first approach the pathogens are treated as a separate species and transport equations are solved to simulate the dose absorption of the pathogen.…”

Geometrical splitting technique to improve the computational efficiency in Monte Carlo calculations for proton therapy

“…The weight window technique is a suitable alternative, but seems to be of limited value in terms of efficiency gain. 19,20 Several efforts have been made to reduce the simulation time in Monte Carlo dose calculation for proton therapy, developing simplified Monte Carlo or hybrid analytical Monte Carlo algorithms 19,[21][22][23] or GPU based algorithms. 24 However, these approaches do not consider the tracking of protons through the treatment head.…”