Relative Biological Effectiveness of Betatron and Conventional X-Radiation on the Regression of Mouse Tumours

THE development of more-powerful sources of X-radiation has made possible the investigation of the biological effectiveness of a variety of ionizing radiations. In vitro experiments have suggested that radiations of higher specific ionization have a greater lethal effect on mouse tumours 1 . We have compared the relative biological effectiveness, on. two types of mouse tumours, of 200-kV. radiations from a conventional X-ray machine with 23.5-MeV. radiations from the University of Saskatchewan betatron.