Neutron Fluence in Antiproton Radiotherapy, Measurements and Simulations

Abstract

Introduction: A significant part of the secondary particle spectrum from antiproton annihilation consists of fast neutrons, which may contribute to a significant dose background found outside the primary beam. Materials and Methods: Using a polystyrene phantom as a moderator, we have performed absolute fluence measurements of the thermalized part of the fast neutron spectrum using Lithium-6 and −7 Fluoride TLD pairs. The results were compared with the Monte Carlo particle transport code FLUKA. Results: The experimental results are found to be in good agreement with simulations. The thermal neutron kerma resulting from the measured thermal neutron fluence is insignificant compared to the contribution from fast neutrons. Discussion: The secondary neutron fluences encountered in antiproton therapy are found to be similar to values calculated for pion treatment, however exact modeling under more realistic treatment scenarios is still required to quantitatively compare these treatment modalities.

Acknowledgements

The work was performed within the AD-4 collaboration and we are grateful to our colleagues for their support. The AD team worked diligently to provide the required antiproton beam and the beam diagnostics data necessary to obtain absolute results. The Danish Cancer Society and the ICE Center under The Danish Science Research Council supported this project with grants. MHH was supported in part by the National Science Foundation under grant CBET-0853157 and by the European Union through a Marie Curie International Incoming Fellowship grant PIIF-GA-2009-234814.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Notes

¹This calculation is for illustration purpose only, actual experiments described here were performed with a 47 MeV antiproton beam.

²http://www.tld.com.pl/

³In the reference simulated by a spherical shell with radii ranging from 6 to 26 cm.