Automatic phase space generation for Monte Carlo calculations of intensity modulated particle therapy

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%.

A phase space model of a Versa HD linear accelerator for application to Monte Carlo dose calculation in a real‐time adaptive workflow

“…These works show that accurate modeling of the linear accelerator head to produce a deterministic phase space is possible. Similar results are also obtained in the field of particle therapy 19,20 …”

“…18 These works show that accurate modeling of the linear accelerator head to produce a deterministic phase space is possible.Similar results are also obtained in the field of particle therapy. 19,20 There is currently considerable interest in fast dose calculation for application to dose reconstruction during adaptive radiotherapy. 21 The goal of this field of research is to be able to display the dose distribution that is being delivered to the patient in near real time, as the patient is being treated, based on real-time imaging systems and either a prior or adaptive treatment plan.Potentially,as the patient's state changes,the imaging system can measure the three-dimensional form of the patient, the tumor can be visualized, the treatment plan adapted as necessary to track the tumor, and the delivered dose reconstructed.…”

Optimization of FLASH proton beams using a track‐repeating algorithm

“…This location excludes the transport of particles through the beam profile monitor and the dose monitors and thus reduces the CPU-time requirements for subsequent simulations. The phase-space file is generated by tuning six parameters 27,29 : Proton mean energy, energy distribution width, spatial distribution widths in the x and y directions, and the cosine of the angle between the particle's traveling direction and the x or y axis distribution widths. We assumed that the energy, the spatial, and the cosine of the angle distributions are all Gaussian.…”

Challenges in Monte Carlo Simulations as Clinical and Research Tool in Particle Therapy: A Review

“…However, even for active scanning techniques applying this method is not straightforward, because of facility dependence of the characteristics of outgoing particles, for instance, due to differences in the beam line devices or differences in operational beam parameters like beam size. In that case, using "optimized" phase space files could be an option [237][238][239], in which the parameters are somehow tuned until the simulations match the measurements (typically longitudinal and lateral dose profiles) at a certain treatment site. This method was recently applied at the Shanghai Proton and Heavy Ion Center [239].…”

“…In that case, using "optimized" phase space files could be an option [237][238][239], in which the parameters are somehow tuned until the simulations match the measurements (typically longitudinal and lateral dose profiles) at a certain treatment site. This method was recently applied at the Shanghai Proton and Heavy Ion Center [239].…”