TRACKING DOWN ALPHA-PARTICLES: THE DESIGN, CHARACTERISATION AND TESTING OF A SHALLOW-ANGLED ALPHA-PARTICLE IRRADIATOR

摘要

Human exposure to alpha-particles from radon and other radionuclides is associated with carcinogenesis, but if well controlled and targeted to cancer cells, alpha-particles may be used in radiotherapy. Thus, it is important to understand the biological effects of alpha-particles to predict cancer risk and optimise radiotherapy. To enable studies of alpha-particles in cells, we developed and characterised an alpha-particle automated irradiation rig that allows exposures at a shallow angle (70 degrees to the normal) of cell monolayers in a 30 mm diameter dish to complement standard perpendicular irradiations. The measured incident energy of the alpha-particles was 3.3 +/- 0.5 MeV (LET in water = 120 keV mu m(-1)), with a maximum incident dose rate of 1.28 +/- 0.02 Gy min(-1), which for a 5 mu m cell monolayer corresponds to a mean dose rate of 1.57 +/- 0.02 Gy min(-1) and a mean LET in water of 154 keV mu m(-1). The feasibility of resolving radiation-induced DNA double-strand breaks (DSB) foci along the track of alpha-particles was demonstrated using immunofluorescent labelling with gamma H2AX and 53BP1 in normal MRC-5 human lung cells.