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J Radiat Res. 2014 Sep;55(5):1028-32. doi: 10.1093/jrr/rru043. Epub 2014 May 29.

RBE and OER within the spread-out Bragg peak for proton beam therapy: in vitro study at the Proton Medical Research Center at the University of Tsukuba.

Author information

  • 1Proton Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan.
  • 2Next Generation Medical Physics Research Program, Research Center for Charged Particle Therapy, National Institute of Radiological Sciences, Inage-ku, Chiba, Japan.
  • 3Proton Medical Research Center, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8575, Japan Department of Radiological Health Science, Institute of Industrial Ecological Sciences, University of Occupational and Environmental Health, Japan, Kitakyushu, Fukuoka, Japan moritake@pmrc.tsukuba.ac.jp.

Abstract

There are few reports on the biological homogeneity within the spread-out Bragg peak (SOBP) of proton beams. Therefore, to evaluate the relative biological effectiveness (RBE) and the oxygen enhancement ratio (OER), human salivary gland tumor (HSG) cells were irradiated at the plateau position (position A) and three different positions within a 6-cm-wide SOBP (position B, 26 mm proximal to the middle; position C, middle; position D, 26 mm distal to the middle) using 155-MeV/n proton beams under both normoxic and hypoxic conditions at the Proton Medical Research Center, University of Tsukuba, Japan. The RBE to the plateau region (RBE(plateau)) and the OER value were calculated from the doses corresponding to 10% survival data. Under the normoxic condition, the RBE(plateau) was 1.00, 0.99 and 1.09 for positions B, C and D, respectively. Under the hypoxic condition, the RBE(plateau) was 1.10, 1.06 and 1.12 for positions B, C and D, respectively. The OER was 2.84, 2.60, 2.63 and 2.76 for positions A, B, C and D, respectively. There were no significant differences in either the RBE(plateau) or the OER between these three positions within the SOBP. In conclusion, biological homogeneity need not necessarily be taken into account for treatment planning for proton beam therapy at the University of Tsukuba.

© The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.

KEYWORDS:

oxygen enhancement ratio; proton; relative biological effectiveness; spread-out Bragg peak

PMID:
24876271
[PubMed - in process]
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