SU-E-J-80: A Simulation Study with Geant4 on the Yields of Positron-Emitting Nuclei (10C, 11C, and 15O) Induced by Protons and Carbon Ions

To study the yields and the depth-distributions of positron-emitting nuclei (PEN) 10C, 11C, and 15O induced by protons and carbon ions in PMMA.

An application built with various physics packages was constructed with Geant4 Monte Carlo Toolkit. A phantom of 15 cm × 15 cm × 50 cm consisting of PMMA (C5H8O2, density 1.18 g/cm³ ) was irradiated with 70, 110 MeV protons and 204 A, 212.12 A MeV carbonions. Beam quality of 1 cm FWHM with 0.2% Gaussian energy spread FWHM was used. For each beam energy, simulation of the energy deposited was recorded for every 1 mm increment of depth in the phantom. The resulting PEN and their yields were recorded at the production point and also at the point of decay in increments of 1 mm.

The overall percentage yields, depth-distributions, and total percentages of PEN per incident particle for both protons and carbon ions were obtained. Our results found that the predominant PMMA fragment was 11C irrespective of incident particle type or energy.

Our yields of PEN are comparable with other simulations (FLUKA and MCHIT) as well as existing experimental data. The present work however overestimates the percentage of PEN in the simulations of incident carbon ions and the percentage of 10C for incident protons compared to the experimental data. This particular application built within the Geant4 Monte Carlo Toolkit can estimate the amount of PEN as well as the depth-distributions of these nuclei in hadron induced radiation therapy.