title: Monte Carlo study of neutron-ambient dose equivalent to patient in treatment room.
abstract: This paper presents an analytical method for the calculation of the neutron ambient dose equivalent H* (10) regarding patients, whereby the different concrete types that are used in the surrounding walls of the treatment room are considered. This work has been performed according to a detailed simulation of the Varian 2300C/D linear accelerator head that is operated at 18MV, and silver activation counter as a neutron detector, for which the Monte Carlo MCNPX 2.6 code is used, with and without the treatment room walls. The results show that, when compared to the neutrons that leak from the LINAC, both the scattered and thermal neutrons are the major factors that comprise the out-of field neutron dose. The scattering factors for the limonite-steel, magnetite-steel, and ordinary concretes have been calculated as 0.91±0.09, 1.08±0.10, and 0.371±0.01, respectively, while the corresponding thermal factors are 34.22±3.84, 23.44±1.62, and 52.28±1.99, respectively (both the scattering and thermal factors are for the isocenter region); moreover, the treatment room is composed of magnetite-steel and limonite-steel concretes, so the neutron doses to the patient are 1.79 times and 1.62 times greater than that from an ordinary concrete composition. The results also confirm that the scattering and thermal factors do not depend on the details of the chosen linear accelerator head model. It is anticipated that the results of the present work will be of great interest to the manufacturers of medical linear accelerators.
authors.affiliation: Energy Engineering and Physics Department, Amir Kabir University of Technology, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Mohammadi
authors.affiliation: Energy Engineering and Physics Department, Amir Kabir University of Technology, Tehran, Iran. Electronic address: hafarideh@aut.ac.ir.
authors.forename: H
authors.initials: H
authors.lastname: Afarideh
authors.affiliation: Radiation Application Group, Shahid Beheshti University, Tehran, Iran.
authors.forename: F
authors.initials: F
authors.lastname: Abbasi Davani
authors.affiliation: College of Information & Communication Engineering, School of Electronics and Electrical Engineering, Sungkyunkwan University, Suwon, Republic of Korea. Electronic address: mitragh@skku.edu.
authors.forename: M
authors.initials: M
authors.lastname: Ghergherehchi
authors.affiliation: Department of Medical Physics, Imam Hosein Hospital, Shahid Beheshti Medical University, Tehran, Iran.
authors.forename: A
authors.initials: A
authors.lastname: Arbabi
mesh_terms: D016477:Artifacts; D003198:Computer Simulation; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006757:Hospital Units; D015233:Models, Statistical; D009010:Monte Carlo Method; D009502:Neutrons; D010315:Particle Accelerators / Q000295:instrumentation*; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D011878:Radiotherapy / Q000295:instrumentation*; D012542:Scattering, Radiation
keywords: Medical linear accelerator; Scattering factor; Thermal factor; Treatment room