@misc{oai:repo.qst.go.jp:00063642,
 author = {Kato, Takamitsu and 加藤 宝光},
 month = {Oct},
 note = {We investigated the biological effects influenced by DNA damage distribution using accelerated heavy charged particles. In order to manipulate DNA damage distribution in nuclei, attached synchronized CHO cells in G1 phase were irradiated either from horizontal or vertical direction to the cell layer. High LET iron ions produced by HIMAC (500MeV/n, LET 200keV/microm) delivered the same dose to cells by irradiating from either directions. Horizontal irradiation produced fewer iron traverses in nuclei, but substantial number of DNA double strand breaks along the tracks (nearly a straight line) was observed. Vertical irradiation produced a greater number of particle hits and evenly distributed DNA damages in nuclei. Interestingly, the colony formation assay revealed that horizontal irradiation is less effective in cell killing with the lower number of chromosome aberrations than vertical irradiation. Intermediate radiosensitivity was observed when suspension cells were irradiated. Although the cell survival curve against the track number for horizontal irradiation is straight line on a log-linear plot, that for vertical irradiation has an initial bend with straight line at higher numbers of tracks. Chromosome aberrations increased linearly with the track number for horizontal irradiation and linear-quadratically for vertical irradiation. These results indicate that the distribution of DNA damage is biologically important for the repair of the damage which affects cell survival. Judging from our data, we hypothesize that vertical irradiation gives slightly higher levels of interactions than horizontal irradiation due to randomly distributed DNA damage to form lethal events. Our results may help design a better protocol for particle therapy, for example, by increasing damage interactions., Radiation research society annual meeting},
 title = {Influence of track directions on the biological consequences in cells irradiated with high LET heavy ions},
 year = {2009}
}