TH‐E‐213AB‐02: Review of the Radiobiological Principles of Radiation Protection

The radiobiological principles underlying radiation protection guidelines will be reviewed, analyzing the published results of the effects of ionizing radiation at the cellular level, in animal experiments and, especially, in epidemiological studies. To ensure a consistent terminology, the radiationdosimetry terms used in radiation biology and in radiation protection will be presented. The concepts of equivalent dose vs dose equivalent as well as the term effective dose, the Gray and Sv units, and the radiation and tissue weighting factors will be explained and illustrated. Human data on radiation induced cancer, including increases in the risk of second cancers following radiation therapy, as well as data on radiation induced tissue reactions, published by the International Commission on Radiological Protection (ICRP), the National Council on Radiation Protection and Measurements (NCRP) and the Biological Effects of Ionizing Radiation (BEIR) Committee, with their latest estimates of risk per unit dose, will be introduced. The dose response of normal tissues will be discussed, including effects on children and the developing embryo and fetus. Recent findings in NCRP and ICRP publications, which include follow up times for some tissues much longer than those common in radiotherapy (up to 20 to 40 versus 5 to 10 years), will be assessed. In particular, current information on acute and chronic radiation syndromes, as well as the newly proposed threshold dose of 0.5 Gy for cataract induction and cardiovascular effects, will be examined. The impact of the new findings and recommendations on the development of radiation protection guidelines and standards, especially in the International Basic Safety Standards on Protection against Ionizing Radiation and for the Safety of RadiationSources (BSS), soon to be adopted world‐wide, will be evaluated. Learning Objectives: 1. To define the radiation protection magnitudes and units, their values and their practical measurement 2. To understand the radiobiological basis of radiation protection standards 3. To distinguish between stochastic effects and tissue reactions