title: Monte Carlo modeling of proton therapy installations: a global experimental method to validate secondary neutron dose calculations.
abstract: Monte Carlo calculations are increasingly used to assess stray radiation dose to healthy organs of proton therapy patients and estimate the risk of secondary cancer. Among the secondary particles, neutrons are of primary concern due to their high relative biological effectiveness. The validation of Monte Carlo simulations for out-of-field neutron doses remains however a major challenge to the community. Therefore this work focused on developing a global experimental approach to test the reliability of the MCNPX models of two proton therapy installations operating at 75 and 178 MeV for ocular and intracranial tumor treatments, respectively. The method consists of comparing Monte Carlo calculations against experimental measurements of: (a) neutron spectrometry inside the treatment room, (b) neutron ambient dose equivalent at several points within the treatment room, (c) secondary organ-specific neutron doses inside the Rando-Alderson anthropomorphic phantom. Results have proven that Monte Carlo models correctly reproduce secondary neutrons within the two proton therapy treatment rooms. Sensitive differences between experimental measurements and simulations were nonetheless observed especially with the highest beam energy. The study demonstrated the need for improved measurement tools, especially at the high neutron energy range, and more accurate physical models and cross sections within the Monte Carlo code to correctly assess secondary neutron doses in proton therapy applications.
authors.affiliation: Institut de Radioprotection et de Sûreté Nucléaire - IRSN/PRP-HOM/SDE/LDRI; BP-17 F-92262 Fontenay-aux-Roses, France.
authors.forename: J
authors.initials: J
authors.lastname: Farah
authors.forename: F
authors.initials: F
authors.lastname: Martinetti
authors.forename: R
authors.initials: R
authors.lastname: Sayah
authors.forename: V
authors.initials: V
authors.lastname: Lacoste
authors.forename: L
authors.initials: L
authors.lastname: Donadille
authors.forename: F
authors.initials: F
authors.lastname: Trompier
authors.forename: C
authors.initials: C
authors.lastname: Nauraye
authors.forename: L
authors.initials: L
authors.lastname: De Marzi
authors.forename: I
authors.initials: I
authors.lastname: Vabre
authors.forename: S
authors.initials: S
authors.lastname: Delacroix
authors.forename: J
authors.initials: J
authors.lastname: Hérault
authors.forename: I
authors.initials: I
authors.lastname: Clairand
mesh_terms: D006801:Humans; D009010:Monte Carlo Method; D009502:Neutrons; D019047:Phantoms, Imaging; D061766:Proton Therapy / Q000295:instrumentation / Q000379:methods*; D011829:Radiation Dosage; D011879:Radiotherapy Dosage