Comparison of GEANT4 Simulations with Experimental Data for Thick Al Absorbers

Abstract

Abstract. Proton beams in medical applications deal with relatively thick targets like the human head or trunk. Therefore, relatively small differences in the total proton stopping power given, for example, by the different models provided by GEANT4 can lead to significant disagreements in the final proton energy spectra when integrated along lengthy proton trajectories. This work presents proton energy spectra obtained by GEANT4.8.2 simulations using ICRU49, Ziegler1985 and Ziegler2000 models for 19.68MeV protons passing through a number of Al absorbers with various thicknesses. The spectra were compared with the experimental data, with TRIM/SRIM2008 and MCNPX2.4.0 simulations, and with the Payne analytical solution for the transport equation in the Fokker-Plank approximation. It is shown that the MCNPX simulations reasonably reproduce well all experimental spectra. For the relatively thin targets all the methods give practically identical results but this is not the same for the thick absorbers. It should be noted that all the spectra were measured at the proton energies significantly above 2MeV, i.e., in the so-called "Bethe-Bloch region". Therefore the observed disagreements in GEANT4 results, simulated with different models, are somewhat unexpected. Further studies are necessary for better understanding and definitive conclusions.

Reduced Calibration Curve for Proton Computed Tomography

“…In particular, we succeed to compare TRIM, MCNPX and GEANT4 simulations with the experimental spectra for a number of Al absorbers with various thicknesses for 19.68 MeV [7] and 49.1 MeV [8] protons passing through, for two Au targets and 49.1 MeV protons [9], and for polyethylene absorber and 25 MeV protons [10].…”