@misc{oai:repo.qst.go.jp:00070881,
 author = {Matsumoto, Kenichiro and Nakanishi, Ikuo and Ueno, Megumi and Anzai, Kazunori and 松本 謙一郎 and 中西 郁夫 and 上野 恵美 and 安西 和紀},
 month = {Sep},
 note = {For improvement of carbon ion beam cancer therapy, low fractionated protocols are planned to reduce mental pain of patients. When clinical dose become higher in future low fractionated protocols, however, generation of reactive oxygen species (ROS) will become un-negligible, although high linear energy transfer (LET) beams have a lower oxygen effect compare to low LET radiations. Very first hydroxyl radical (*OH) can be generated by radiolysis of water molecules. It may be presumed that generation of high density OH localized on the truck of carbon ion beam. In this study, distribution and density of *OH caused in an aqueous gelatin sample irradiated by carbon ion beam was investigated.
Reaction mixtures containing several concentrations (7.7--1650 mM) of DMPO was prepared. The reaction mixtures were irradiated by 290 MeV carbon mono beam using HIMAC (Heavy-Ion Medical Accelerator in Chiba, National Institute of Radiological Sciences), applying several LET (20 to 180 keV/mu-m). The dose was 32 Gy. An aliquot (100 mu-L) of reaction mixture was sampled into a PTFE tubing. DMPO-OH (spin trapped *OH) generated in the reaction mixture was measured by X-band EPR spectrometer (JEOL). The experiments were repeated using X-ray for a comparison. X-ray irradiation was performed using PANTAK 320S (Shimadz). The reaction mixtures were irradiated with 32 Gy X-ray (Eeff = 80 keV) at a dose rate of 3.3 Gy/min.
The EPR signal intensity of DMPO-OH in X-ray-irradiated sample was increased with concentration of DMPO added, then looks reached plateau around 1.6 mM DMPO. The concentration of DMPO-OH at the plateau level was around 30 mu-M. For carbon-ion beam, amount of DMPO-OH in the sample did not show obvious plateau and increased with DMPO concentration until 1650 mM. The result suggests that *OH generation around the truck of carbon ion beam was much dense compared with X-ray., The 16th biennial meeting for the Society for Free Radical Research International (SFRRI2012)},
 title = {Density of Hydroxyl Radical Generated in an Aqueous Solution Irradiated by Carbon Ion Beam},
 year = {2012}
}