抄録
A single cell irradiation system has been developed at JAERI-Takasaki to study radiobiological processes in single-ion-hit mammalian cells and bystander cells, in ways that cannot be achieved using conventional broad field exposures. Individual mammalian cultured cells are irradiated in the atmosphere on the cell dish, the bottom of which is made of ion-track-detector CR-39, with a single or precise numbers of 13.0 MeV/u 20Ne and 11.5 MeV/u 40Ar ions. Targeting and irradiation of the cells are performed automatically at the on-line microscope of the microbeam apparatus according to the positional data of the target cells obtained at the off-line microscope before irradiation. However, previously used automatic stages had a potential inaccuracy of stage movement, which affected greatly on the overall targeting and revisiting accuracy. Thus we replaced the automatic stages and measured the improvement of the mechanical accuracy of cell targeting system; object finding and retargeting accuracy using pseudo-cell sample, and accuracy of ion traversal on targeted cells. The samples irradiated with 5 count of 40Ar ions using old stages included more than 25% of fail-to-hit cells. On the contrary, the distribution of ion-hits with the new stages indicated that 70% of cells were irradiated with 3-5 ions and less than 5% of cells were failed to hit.
