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Enhanced radiobiological effects at the distal end of a clinical proton beam : in vitro study

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Title: Enhanced radiobiological effects at the distal end of a clinical proton beam : in vitro study
Authors: Matsumoto, Yoshitaka Browse this author
Matsuura, Taeko Browse this author →KAKEN DB
Wada, Mami Browse this author
Egashira, Yusuke Browse this author
Nishio, Teiji Browse this author
Furusawa, Yoshiya Browse this author
Keywords: proton beam
biological effectiveness
distal end
cell survival
spread-out Bragg-peak
Issue Date: 1-Jul-2014
Publisher: Oxford University Press
Journal Title: Journal of Radiation Research
Volume: 55
Issue: 4
Start Page: 816
End Page: 822
Publisher DOI: 10.1093/jrr/rrt230
Abstract: In the clinic, the relative biological effectiveness (RBE) value of 1.1 has usually been used in relation to the whole depth of the spread-out Bragg-peak (SOBP) of proton beams. The aim of this study was to confirm the actual biological effect in the SOBP at the very distal end of clinical proton beams using an in vitro cell system. A human salivary gland tumor cell line, HSG, was irradiated with clinical proton beams (accelerated by 190 MeV/u) and examined at different depths in the distal part and the center of the SOBP. Surviving fractions were analyzed with the colony formation assay. Cell survival curves and the survival parameters were obtained by fitting with the linear?quadratic (LQ) model. The RBE at each depth of the proton SOBP compared with that for X-rays was calculated by the biological equivalent dose, and the biological dose distribution was calculated from the RBE and the absorbed dose at each position. Although the physical dose distribution was flat in the SOBP, the RBE values calculated by the equivalent dose were significantly higher (up to 1.56 times) at the distal end than at the center of the SOBP. Additionally, the range of the isoeffective dose was extended beyond the range of the SOBP (up to 4.1 mm). From a clinical point of view, this may cause unexpected side effects to normal tissues at the distal position of the beam. It is important that the beam design and treatment planning take into consideration the biological dose distribution.
Type: article
Appears in Collections:国際連携研究教育局 : GI-CoRE (Global Institution for Collaborative Research and Education : GI-CoRE) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 松浦 妙子

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