Abstract
The use of microbeams for partial-cell irradiation, the selective exposure of microscopic fractions of living cells to ionizing radiation or UV light, has a long history. The early work used a microbeam as a tool for microsurgery to analyze their normal function of various cell parts. Later, as interest in the effects of ionizing radiation itself developed, these techniques were used as a radiobiological tool which yields information about the mechanisms of cellular radiation responses by determining which part of a cell was most sensitive to radiation damage. The earliest particle microbeam experiments were performed in 1953 using a 2 MV Van de Graaff accelerator and micro collimators to form a proton microbeam. In the next decade, an 11 MeV/amu proton and 22 MeV/amu deuteron microbeam was developed using a cyclotron. These earlier microbeam systems were helpful in studying radiation effects in living systems, especially to show that damage to the cytoplasm had a very limited effect on the survival of the cell. However, these systems were limited at relatively high doses. To investigate the effects at lower doses, it is necessary to establish single particle irradiation technique. After in 1990s, single-particle microbeams were developed in several facilities for targeting cells individually with a specific numbers of protons or heavy ions to elucidate the radiobiological processes in hit cells and bystander cells, in ways that cannot be achieved using conventional broad-field exposures.
