title: The FiR 1 photon beam model adjustment according to in-air spectrum measurements with the Mg(Ar) ionization chamber.
abstract: The mixed neutron-photon beam of FiR 1 reactor is used for boron-neutron capture therapy (BNCT) in Finland. A beam model has been defined for patient treatment planning and dosimetric calculations. The neutron beam model has been validated with an activation foil measurements. The photon beam model has not been thoroughly validated against measurements, due to the fact that the beam photon dose rate is low, at most only 2% of the total weighted patient dose at FiR 1. However, improvement of the photon dose detection accuracy is worthwhile, since the beam photon dose is of concern in the beam dosimetry. In this study, we have performed ionization chamber measurements with multiple build-up caps of different thickness to adjust the calculated photon spectrum of a FiR 1 beam model.
authors.affiliation: Department of Physics, University of Helsinki, POB 64, FI-00014, Finland; HUS Medical Imaging Center, Helsinki University Central Hospital, FI-00029 HUS, Finland. Electronic address: hanna.koivunoro@helsinki.fi.
authors.forename: H
authors.initials: H
authors.lastname: Koivunoro
authors.affiliation: Institute for Nuclear Chemistry, University of Mainz, D-55099 Mainz, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Schmitz
authors.affiliation: HUS Medical Imaging Center, Helsinki University Central Hospital, FI-00029 HUS, Finland.
authors.forename: E
authors.initials: E
authors.lastname: Hippeläinen
authors.affiliation: Nuclear Science and Technology Development Center, National Tsing Hua University, HsinChu, Taiwan.
authors.forename: Y-H
authors.initials: YH
authors.lastname: Liu
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, Finland.
authors.forename: T
authors.initials: T
authors.lastname: Serén
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, Finland.
authors.forename: P
authors.initials: P
authors.lastname: Kotiluoto
authors.affiliation: VTT Technical Research Centre of Finland, Espoo, Finland.
authors.forename: I
authors.initials: I
authors.lastname: Auterinen
authors.affiliation: Department of Physics, University of Helsinki, POB 64, FI-00014, Finland; HUS Medical Imaging Center, Helsinki University Central Hospital, FI-00029 HUS, Finland.
authors.forename: S
authors.initials: S
authors.lastname: Savolainen
mesh_terms: D000388:Air; D016754:Boron Neutron Capture Therapy / Q000295:instrumentation*; D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D015233:Models, Statistical; D009688:Nuclear Reactors / Q000295:instrumentation*; D017785:Photons / Q000627:therapeutic use*; D011874:Radiometry / Q000295:instrumentation* / Q000379:methods*; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
keywords: BNCT; Dosimetry; Ionization Chamber; MCNP5; Monte Carlo; Penelope