title: Evaluation of neutron dose equivalent from the Mevion S250 proton accelerator: measurements and calculations.
abstract: Neutron production is of concern for proton therapy, especially for passive scattering proton beam delivery methods. The levels of neutron dose equivalent vary significantly with system design and treatment parameters. The purpose of this study was to examine neutron dose equivalent per therapeutic dose (H/D) around the Mevion S250 proton therapy system, a novel design of proton therapy systems. The benchmark comparisons between measurement and simulation were found to be within a factor of 2 for most cases. The H/D values were evaluated as a function of various parameters. The results showed that, at a standard reference condition (10 × 10 cm(2) field size, distance 1 m detector-to-isocenter lateral to the primary proton beam direction), the H/D values range from 0.72 to 3.37 mSv Gy(-1) for all configurations studied. The H/D values generally (1) decreased as the neutron detectors moved away from the isocenter, (2) decreased with increasing aperture field sizes, (3) increased with increasing angle from the initial beam axis and (4) were independent of treatment nozzle position. The H/D trends were consistent with other existing passive scattering proton accelerators reported in the literature.
authors.affiliation: Department of Radiation Oncology, Washington University, Saint Louis, MO, USA.
authors.forename: Kuan Ling
authors.initials: KL
authors.lastname: Chen
authors.forename: Charles D
authors.initials: CD
authors.lastname: Bloch
authors.forename: Patrick M
authors.initials: PM
authors.lastname: Hill
authors.forename: Eric E
authors.initials: EE
authors.lastname: Klein
mesh_terms: D004781:Environmental Exposure / Q000032:analysis; D006801:Humans; D009010:Monte Carlo Method; D009502:Neutrons; D010315:Particle Accelerators; D061766:Proton Therapy / Q000009:adverse effects; D011522:Protons / Q000009:adverse effects*; D011829:Radiation Dosage; D011874:Radiometry
chemical_list: D011522:Protons