Dose Fractionation Concept in Radiation Protection to Standardize Risk/Dose Limits and Epidemiology Studies

Ionizing radiation, either originated from natural background (NBG) radiation sources (primordial radioactive materials in the earth crust and cosmic rays) or from man-made sources (reactors, accelerators, diagnostic and radiotherapy equipment, industrial sources, etc.) expose the public and workers (as members of public) which may cause chemical and biological changes in the human body cells and may damage them temporarily or permanently [1]. Some cells may die (apoptosis), some become abnormal either temporarily or permanently, or some have damages in the DNA as a genetic material which may cause cancer. The cell may also make self-repair depending on the severity of the damage and continue survival like a normal cell. The extent of the damage to the cells depends on many radiation exposure factors such as the radiation type and its energy, LET, dose and dose rate, type of cell at risk and its sensitivity, cell oxygenation, environmental conditions, and whether or not the dose delivered to the cells is continuous or “fractionated” over time, a concept which has not been considered in the field of “radiation protection” so far.