Purpose To systematically evaluate simulated characteristic multiple Coulomb scattering (MCS) angles with GATE/Geant4 against experimental data for 158.6 MeV proton beams. Methods The open source toolkit GATE alongside Geant4 in release 9.5 patch 02, 9.6 patch 03, 10.0 patch 02, 10.1, and 10.2 patch 02 were used to simulate a 158.6 MeV collimated monoenergetic proton beam impinging on a scattering disc of various materials and thicknesses: in total 144 different set-ups were investigated per Geant4 release and compared to measured data. Data was read out into a phase space providing information of individual particle momentum. For analysis a one dimensional Gaussian was fit to the beam profile and the multiple Coulomb scattering angles were calculated using the ROOT toolkit. Results The agreement between simulated and experimental data was found to be dependent on the Geant4 release. On average an agreement of - 1.1 % with a standard deviation of 3.4 % was reached with Geant4 release 10.2. Increased differences were found for very thick targets close to the particle range and for older Geant4 versions employing the previous electromagnetic model, Urban MCS. Conclusion Multiple Coulomb scattering algorithms implemented in the latest Geant4 releases and in particular Geant4.10.2 showed a very satisfactory agreement with measured data for applications in proton pencil beam scanning.
