title: An investigation of the alternating fractionation formula of the Cumulative Radiation Effect.
abstract: The alternating fractionation formula of the Cumulative Radiation Effect (CRE) system was investigated using the mouse intestinal crypt system as a method of assessment of the amount of radiation damage in a normal tissue. The experimental results revealed that the formula is correct in predicting an increased effect with alternating large and small sized fractions, when compared with a standard schedule where the fraction size was kept constant but achieved the same total dose. However, the results also demonstrated that the order in which the alternate fractions were administered affected the amount of radiation damage produced in the tissue. This observation is in contradiction to another prediction of the formula, that the order in which equal numbers of fractions of different magnitudes are administered, will have no effect on the biological end point. The formula, therefore, is only an approximate model of radiation damage in normal tissue and much more information is required before it can be improved upon.
mesh_terms: D000818:Animals; D002455:Cell Division; D002470:Cell Survival; D005720:Gamma Rays; D007421:Intestine, Small / Q000473:pathology / Q000528:radiation effects*; D007700:Kinetics; D051379:Mice; D008954:Models, Biological; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000473:pathology; D011878:Radiotherapy / Q000379:methods; D013997:Time Factors