Aim: The purpose of this work is to evaluate the precision with which the GEANT4 toolkit simulates the production of β+ emitters relevant for in-beam and real-time PET in proton therapy.
Background: An important evolution in proton therapy is the implementation of in-beam and real-time verification of the range of protons by measuring the correlation between the activity of β+ and dose deposition. For that purpose, it is important that the simulation of the various β+ emitters be sufficiently realistic, in particular for the 12N short-lived emitter that is required for efficient in-beam and real-time monitoring.
Methods: The GEANT4 toolkit was used to simulate positron emitter production for a proton beam of 55 MeV in a cubic PMMA target and results are compared to experimental data.
Results: The three β+ emitters with the highest production rates in the experimental data (11C, 15O and 12N) are also those with the highest production rate in the simulation. Production rates differ by 8% to 174%. For the 12N isotope, the β+ spatial distribution in the simulation shows major deviations from the data. The effect of the long range (of the order of 20 mm) of the β+ originating from 12N is also shown and discussed.
Conclusions: At first order, the GEANT4 simulation of the β+ activity presents significant deviations from the data. The need for precise cross-section measurements versus energy below 30 MeV is of first priority in order to evaluate the feasibility of in-beam and real-time PET.
Keywords: activity distribution; GEANT4 toolkit; Positron emitters; Proton therapy.
Copyright © 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.