The variation in biological effectiveness of X-rays and gamma rays with energy.
The ICRP has attributed the same relative risk for all low-LET (linear energy transfer) radiations, including X and gamma radiations of all energies. However, very low energy X-rays are expected to be more biologically effective, per unit absorbed dose, than high energy X-rays or gamma rays due to the production of lower energy secondary electrons, with a correspondingly higher LET. This increase in relative biological effectiveness (RBE) is also seen experimentally for a range of biological end-points, however, a wide range of RBE values have been reported. The assessment of risks is particularly important due to the use of low energy X-rays for mammography screening. A review of the published data on the variation in biological effectiveness with energy is presented here.
Hill
M A
MA
MRC Radiation and Genome Stability Unit, Harwell, Oxfordshire OX11 0RD, UK. m.hill@har.mrc.ac.uk
D000818:Animals; D002869:Chromosome Aberrations; D005720:Gamma Rays; D006801:Humans; D018499:Linear Energy Transfer; D008327:Mammography; D009154:Mutation; D017785:Photons; D012062:Relative Biological Effectiveness; D014965:X-Rays