Distributions of positron-emitting nuclei in proton and carbon-ion therapy studied with GEANT4

Abstract

Depth distributions of positron-emitting nuclei in PMMA phantoms are calculated within a Monte Carlo model for heavy-ion therapy (MCHIT) based on the GEANT4 toolkit (version 8.0). The calculated total production rates of 11C, 10C and 15O nuclei are compared with experimental data and with corresponding results of the FLUKA and POSGEN codes. The distributions of e+ annihilation points are obtained by simulating radioactive decay of unstable nuclei and transporting positrons in the surrounding medium. A finite spatial resolution of the positron emission tomography (PET) is taken into account in a simplified way. Depth distributions of β+-activity as seen by a PET scanner are calculated and compared to available data for PMMA phantoms. The obtained β+-activity profiles are in good agreement with PET data for proton and 12C beams at energies suitable for particle therapy. The MCHIT capability to predict the β+-activity and dose distributions in tissue-like materials of different chemical composition is demonstrated.For more information on this article, see medicalphysicsweb.org