title: Characterization of neutron beams for boron neutron capture therapy: in-air radiobiological dosimetry.
abstract: The survival curves and the RBE for the dose components generated in boron neutron capture therapy (BNCT) were determined separately in neutron beams at Japan Research Reactor No. 4. The surviving fractions of V79 Chinese hamster cells with or without 10B were obtained using an epithermal neutron beam (ENB), a mixed thermal-epithermal neutron beam (TNB-1), and a thermal (TNB-2) neutron beam; these beams were used or are planned for use in BNCT clinical trials. The cell killing effect of the neutron beam in the presence or absence of 10B was highly dependent on the neutron beam used and depended on the epithermal and fast-neutron content of the beam. The RBEs of the boron capture reaction for ENB, TNB-1 and TNB-2 were 4.07 +/- 0.22, 2.98 +/- 0.16 and 1.42 +/- 0.07, respectively. The RBEs of the high-LET dose components based on the hydrogen recoils and the nitrogen capture reaction were 2.50 +/- 0.32, 2.34 +/- 0.30 and 2.17 +/- 0.28 for ENB, TNB-1 and TNB-2, respectively. The RBEs of the neutron and photon components were 1.22 +/- 0.16, 1.23 +/- 0.16, and 1.21 +/- 0.16 for ENB, TNB-1 and TNB-2, respectively. The approach to the experimental determination of RBEs outlined in this paper allows the RBE-weighted dose calculation for each dose component of the neutron beams and contributes to an accurate inter-beam comparison of the neutron beams at the different facilities employed in ongoing and planned BNCT clinical trials.
authors.affiliation: Department of Neurosurgery, Institute of Clinical Medicine, University of Tsukuba, Tsukuba City, Ibaraki, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Akira
authors.initials: A
authors.lastname: Matsumura
authors.forename: Kazuyoshi
authors.initials: K
authors.lastname: Yamamoto
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Kumada
authors.forename: Naohiko
authors.initials: N
authors.lastname: Hori
authors.forename: Yoshiya
authors.initials: Y
authors.lastname: Torii
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Shibata
authors.forename: Tadao
authors.initials: T
authors.lastname: Nose
mesh_terms: D000388:Air; D000818:Animals; D016754:Boron Neutron Capture Therapy / Q000295:instrumentation* / Q000379:methods*; D016466:CHO Cells; D002986:Clinical Trials as Topic; D006224:Cricetinae; D009502:Neutrons; D017785:Photons; D011874:Radiometry; D013997:Time Factors