PNNL

Abstract

The bystander effect, responses of cells not traversed by particles of a radiation field, has generated a flurry of activity in the radiation biology community. The conventional wisdom that health risks are determined by the response of individual cells to DNA damage is being challenged. Much of the current data on bystander effects was obtained in experiments with high LET radiation where most of the cells are bystanders and their responses are more easily observed. Even at a low fluence, radiation fields composed of low-LET particles tend to produce a uniform distribution of dose at the cellular level, which makes bystanders more difficult to identify. Despite these difficulties, experimental results on bystander effects induced by low-LET radiation are becoming available through application of focused x-ray sources (1) and electron microbeams (2). We have applied Monte Carlo track-structure simulations (3) to calculate microdosimetric quantities that are useful in the design of experiments with these facilities.