PNNL

Abstract

Several laboratories are using microbeams to characterize bystander responses induced by low-LET radiation. This paper describes dosimetry calculations supporting the design of low-LET microbeams and the interpretation of data obtained from these facilities. One approach to low-LET microbeam irradiation is to place a mask with micron-size holes over an electron gun (see Resat et al. in these proceedings). Monte Carlo simulations by Miller et al. (1) suggested that individual mammalian cells in a confluent monolayer could be targeted for irradiation by 25 to 100 keV electrons with minimal dose leakage to their neighbors. The PITS (2) code set was used to generate electron tracks by introducing a monoenergetic delta-ray source module. Tracks simulated in a uniform water medium were scored in a simple model that assumed the target cell was cylindrically symmetric and had concentric cytoplasm and nucleus. Radial profiles, the lateral extent of cytoplasm and nucleus as a function of depth into a cell, were obtained from confocal microscopy of HeLa-cell monolayers.