Automatic phase space generation for Monte Carlo calculations of Intensity Modulated Particle Therapy

TL;DR

This paper introduces an automated algorithm for generating phase space files in Monte Carlo dose calculations for particle therapy, improving efficiency and accuracy in beam modeling compared to manual parameter determination.

Contribution

We developed an automatic, efficient algorithm to generate phase space parameters for Monte Carlo simulations, enhancing dose calculation accuracy in particle therapy.

Findings

Gamma-index > 96% for dose distribution comparison

Mean lateral spot size difference < 3.5% at multiple depths

Automated PS generation matches measurements effectively

Abstract

Monte Carlo (MC) is generally considered as the most accurate dose calculation tool for particle therapy. However, a proper description of the beam particles kinematics is a necessary input for a realistic simulation. Such a description can be stored in phase space (PS) files for different beam energies. A PS file contains kinetic information such as energies, positions and travelling directions for particles traversing a plane perpendicular to the beam direction. The accuracy of PS files play a critical role in the performance of the MC method for dose calculations. A PS file can be generated with a set of parameters describing analytically the beam kinematics. However, determining such parameters can be tedious and time consuming. Thus, we have developed an algorithm to obtain those parameters automatically and efficiently. In this paper, we present such an algorithm and compare dose calculations using PS automatically generated for the Shanghai Proton and Heavy Ion Center (SPHIC) with measurements. The gamma-index for comparing calculated depth dose distributions (DDD) with measurements are above 96.0% with criterion 0.6%/0.6 mm. For each single energy, the mean difference percentage between calculated lateral spot sizes at 5 different depths and measurements are below 3.5%.