The Auger electron effect in radiation dosimetry - A review

Radionuclides that emit Auger electrons are widely used in nuclear medicine and biomedical research. The Auger emitting radionuclides give off a cascade of low energy electrons, the total energy of which is deposited within some nanometers; the local dose is therefore very high. If the radionuclide is part of a chemical compund which forms a DNA base analogue or which preferentially enters the cell nucleus, the biological effects of the Auger electrons to the DNA or the nucleus can be as severe as from high-LET alpha particles. Neither the recommendations of the International Commission on Radiological Protection (ICRP) in Publication No. 60, nor the International Basic Safety Standards for Protection against Ionizing Radiation and for the Safety of Radiation Sources provide any guidance on calculating the equivalent dose for these radionuclides. For the radiation weighting factor of electrons (value 1) they recommend excluding the Auger electrons emitted from nuclei bound to DNA. However, recently a Task Group of the American Association of Physicists in Medicine (AAPM) has proposed that the component of dose from the Auger electrons for radionuclides bound to DNA be given a preliminary radiation weighting factor of of 10 for deterministic effects and 20 for stochastic effects. The dose equivalent calculated with these weighting factors must be modulated by experimentally determined subcellular distributions.