title: Neutron shielding for a new projected proton therapy facility: A Geant4 simulation study.
abstract: In this work, we used the Monte Carlo-based Geant4 simulation toolkit to calculate the ambient dose equivalents due to the secondary neutron field produced in a new projected proton therapy facility. In particular the facility geometry was modeled in Geant4 based on the CAD design. Proton beams were originated with an energy of 250MeV in the gantry rooms with different angles with respect to the patient; a fixed 250MeV proton beam was also modeled. The ambient dose equivalent was calculated in several locations of interest inside and outside the facility, for different scenarios. The simulation results were compared qualitatively to previous work on an existing facility bearing some similarities with the design under study, showing that the ambient dose equivalent ranges obtained are reasonable. The ambient dose equivalents, calculated by means of the Geant4 simulation, were compared to the Australian regulatory limits and showed that the new facility will not pose health risks for the public or staff, with a maximum equivalent dose rate equal to 7.9mSv/y in the control rooms and maze exit areas and 1.3·10-1mSv/y close to the walls, outside the facility, under very conservative assumptions. This work represents the first neutron shielding verification analysis of a new projected proton therapy facility and, as such, it may serve as a new source of comparison and validation for the international community, besides confirming the viability of the project from a radioprotection point of view.
authors.affiliation: Politecnico di Milano, Dipartimento di Energia, Via La Masa 34, I-20156 Milano, Italy; Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia. Electronic address: francesco.cadini@polimi.it.
authors.forename: Francesco
authors.initials: F
authors.lastname: Cadini
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia.
authors.forename: David
authors.initials: D
authors.lastname: Bolst
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia; Illawarra Health Medical Research Institute, University of Wollongong, NSW, Australia.
authors.forename: Susanna
authors.initials: S
authors.lastname: Guatelli
authors.affiliation: Mayo Clinic, Rochester, MN, USA.
authors.forename: Chris
authors.initials: C
authors.lastname: Beltran
authors.affiliation: Department of Radiation Oncology, Prince of Wales Hospital, Randwick, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Jackson
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, NSW, Australia; Illawarra Health Medical Research Institute, University of Wollongong, NSW, Australia.
authors.forename: Anatoly B
authors.initials: AB
authors.lastname: Rosenfeld
mesh_terms: D009010:Monte Carlo Method; D009502:Neutrons; D019047:Phantoms, Imaging; D061766:Proton Therapy / Q000009:adverse effects / Q000295:instrumentation*; D011835:Radiation Protection
keywords: Geant4; Neutron shielding; Proton therapy facility; Radiation protection