Microbeam Radiation Biology

The understanding of radiation effects has been driven by experimental studies in a range of in vitro and in vivo models, including human exposures. These have, for external beam exposures, predominantly utilized conventional radiation sources where uniform exposures of the target of interest have been used. Ionizing radiations deliver their energy in a quantized way via the production of tracks of electrons or charged particles. The doses from these various sources are very low and generally of low dose rate. At the level of individual cells within the human body, this can equate to only single tracks of radiation crossing a cell over periods of weeks or years. Our understanding of the effects of these low doses requires technological approaches which can deliver highly localized radiation beams into biological models and has been an underpinning rational for the development of microbeams as key experimental tools. Here, we outline key characteristics of charged particle, x-ray, and electron microbeams and contrast them with laser-based approaches. We discuss the physical qualities of these sources and review biological studies involving low dose studies, subcellular targeting, and bystander responses.