Why This Project?

Radiation, such as x-rays, produces biological damage in both "hit" and unscathed cells in the same neighborhood. These cells can be damaged even when they are not directly hit by the radiation. This effect is called the "bystander effect". At low radiation doses, in fact, most cells are not directly hit by radiation, so these effects could have profound implications for estimating the risks of low levels of radiation. In other words, cells that are damaged by radiation can send out signals to neighboring cells that are not hit, and this signal can result in biological damage to the neighboring cell. We have already developed some biologically-based understanding of these "bystander" effects. At present our understanding is limited to fairly high doses of a particular type of radiation, given over a very short period of time.

Project Goals:

1. Continue to develop theories of bystander processes, and see how important they might be for radiation risks at very low doses.
   
2. Extend our understanding of bystander effects to lower radiation doses, to different radiation types (such as x rays), and to longer radiation exposure times.

Research Approach:

Work from many laboratories covering a broad spectrum of biological endpoints has shown these bystander effects. One really useful tool that we use to study these bystander effects is a so called "microbeam" in which a single cell can be irradiated without any stray radiation reaching other nearby cells.

Expected Outcomes:

1. An improved biophysical model of bystander effects, which we will refine using experimental results both from our own experiments as well from other laboratories.
   
2. These models will be used to make an overall best assessment of the public-health significance of bystander-mediated responses at low doses for different types of radiation, delivered at low and high dose rates.