The Use of Microbeams in Radiation Biology: An Overview

摘要

In recent years, there has been a resurgence in the use of microbeams in radiation biology. Three main research needs have underpinned this development: 1) The need to understand radiation effects at the level of a single particle traversal of relevance to radiation risk. Low-dose studies with conventional particle beams are complicated by the Poisson distribution such that the best that can be achieved is an average on one particle traversal; i.e., 37% of the population receive no hits, 37% 1 hit, and 26% greater than 1 hit. 2) The importance of understanding the distribution of radiosensitivity'' across the cell nucleus and the cell in general, to determine where critical targets and processes are located. 3) The ability to target individual cells within a population and determine responses of relevance to the in vivo situation involving cell-cell communication. Recent technological developments, such as improved imaging techniques, microengineering and radiation detector technologies and the major advances in cell biology techniques, which allow one to measure effects at the single-cell level, have generated new interest in this area. Microbeams are an example of several approaches designed to target radiation to regions of cells or tissues. Other approaches include: 1) The use of biostacks, which involves recording the positions of particle traversals using track-etch techniques and relating these to the positions of the cells growing on these detectors. This approach has already been used in several studies determining cell survival to low doses of a particles with a view to measuring the effects of a single particle traversal. 2) Targeting of radioisotopes into specific molecules within cells. For example, ~(125)IdUrd to target DNA and the cell nucleus and ~(125)I-concanavalin A to target the cell membrane and cytoplasm. Other approaches currently in clinical trials include boron neutron capture studies where epithermal neutrons are used to target boronated compounds in tumour cells, leading to the production of short-range a particles and ~7Li particles. 3) Another approach that has been used successfully is to target groups of cells within a population using a grid which shields a known fraction of the dish being exposed. This approach has the advantage of being able to allow large numbers of cells to be exposed quickly, but the disadvantage of not being able to specify the region within cells which is irradiated.