ESTRO 38 Abstract book

S480 ESTRO 38

Düsseldorf HHU, Physics, Medical Physics, Germany ; 5 German Cancer Consortium DKTK, Radiation Oncology and Imaging, Heidelberg, Germany ; 6 University Hospital Essen, Department of Particle Therapy, Essen, Germany Purpose or Objective PENH is a recently coded module for simulation of proton transport in conjunction with the Monte Carlo (MC) code PENELOPE [1]. The purpose of this work is to benchmark this module. PENH uses calculated differential cross sections for proton elastic collisions that include electron screening effects as well as nuclear structure effects. Proton-induced nuclear reactions are simulated from information in the ENDF-6 database [2], or from alternative nuclear databases in ENDF format (e.g., TENDL-2017). Material and Methods Results from simulations with PENH are compared with simulation data obtained from TOPAS MC v3.1p2 [3] and RayStation 6 MC [4]. In all simulations a measurement- derived Fermi-Eyges [5] beam model, with nominal energy 225 MeV, was used. The beam model reproduced the phase-space of an IBA pencil beam (PB) scanning dedicated nozzle. The simulated geometry consisted of a water phantom with a 50 cm-thick layer of air upstream of it. Simulated dose results were compared to experimental data obtained with the MatriXX PT 2D detector (IBA Dosimetry) [6]. Results Depth dose profiles taken at varying radius from the central axis are shown in figure 1. The radial distance from the central axis at which the profiles are plotted appears above of each subfigure. All plots shown are normalized to the central axis dose at a depth of 3 cm. Excellent agreement is observed among the evaluated codes with the experimental data up to 3 cm from the central axis, that is, at the halo region where the dose drops three orders of magnitude from the maximum dose. Results from RayStation MC were smoothed with a moving average filter. Results from TOPAS MC coincide with experimental data up to six orders of magnitude below the maximum. Results from both RayStation and PENH qualitatively reproduce the experimental behavior in the low dose regions from three to six orders of magnitude below the maximum.

Conclusion The outstanding agreement between TOPAS MC and experimental data is partly due to the fact that TOPAS MC takes into account neutron transport and PENH does not. However, the differences in the results produced by both codes cannot be fully adscribed to neutron simulation. They arise from the different physics models and tracking schemes. We conclude that the elaborate physics modeling of the PENELOPE/PENH code yields results consistent with measurements. [1] F. Salvat and J. M. Quesada, “Nuclear effects in proton transport and dose calculations” (to be published). [2] M. Herman and A. Trkov, ENDF-6 Formats Manual Nuclear Energy Agency July, 2010. [3] Perl J et al. TOPAS: an innovative proton Monte Carlo platform for research and clinical applications Med. Phys. 39 6818–37, 2012. [4] RaySearch Laboratories AB, Schweden. RAYSTATION 6 Reference Manual. RSL-DRS-6.0-REF-EN-1.0-2016-12-22, Dezember 2016. [5] B. Gottschalk. Techniques of proton radiotherapy: transport theory, arXiv:1204.4470v2 , 2012. [6] IBA Dosimetry GmbH, Schwarzenbruck. MatriXX PT User's Guide. P-09-005-510-002 01, August 2012. PO-0905 Validation of a 4D Monte Carlo optimization and planning feature for CyberKnife lung treatment S. Trivellato 1,2 , E. Rondi 1 , S. Vigorito 1 , E. Miglietta 3 , F. Castellini 3 , G. Piperno 3 , A. Ferrari 3 , B.A. Jereczek- Fossa 3,4 , F. Cattani 1 1 IEO- European Institute of Oncology IRCCS, Unit of Medical Physics, Milan, Italy ; 2 University of Milan, Department of Physics, Milan, Italy ; 3 IEO- European Institute of Oncology IRCCS, Division of Radiation Oncology, Milan, Italy ; 4 University of Milan, Department of Oncology and Hemato-oncology, Milan, Italy Purpose or Objective In thorax treatments, the management of respiratory motion is mandatory. An available treatment planning