Heavy-ion microbeams--development and applications in biological studies

High-linear-energy-transfer (LET) heavy charged particle radiation has been used in radiotherapy and radiation breeding because of its greater biological effectiveness compared with low-LET radiation. The health risk assessment for astronauts due to space radiation during interplanetary manned missions is also an important issue concerning the biological effects of heavy-ion radiation. Localized irradiation of specific regions within organisms using heavy-ion microbeam systems provides an attractive means of investigating the mechanism of heavy-ion radiation action. In addition, heavy-ion microbeams can be used as a radio-microsurgical tool for analyzing a broad range of biological phenomena. This paper reviews briefly the current status concerning the development of heavy-ion microbeams for use on living organisms with particular emphasis on its applications in biological studies in eukaryotes including plants, silkworm, nematode, and cultured plant and mammalian cells. Heavy-ion-induced bystander effects and its LET dependency will also be addressed. Index Terms--Biological applications, heavy-ion microbeam, microbeam apparatus.