title: Radiation-induced hemopoietic death in mice as a function of photon energy and dose rate.
abstract: Radiation-induced hemopoietic death was measured in mice exposed to photons of four different energies: 250-kVp X rays, 60Co gamma rays (1.25 MeV), and 6- and 25-MV photons from a linear accelerator. For each radiation source, the lethal dose which killed 50% of the population in 30 days (LD50/30) associated with the hemopoietic syndrome was determined in groups of mice exposed to graded doses from 600 to 1150 cGy at dose rates of 20, 40, and 80 cGy/min. The calculated LD50/30 values for 25 and 6 MV were significantly different from each other at all exposure rates while no difference was observed between 6 MV and 60Co. Using 60Co gamma rays as the standard, the relative biologic effectiveness was as follows: 250 kVp greater than 25 MV greater than 6 MV = 60Co. The data suggest that there may be a greater damage to tissue within the marrow cavities following exposure to very high megavoltage radiation, a factor which must be considered with the increasing utilization of linear accelerators in the clinic and laboratory.
mesh_terms: D000818:Animals; D003037:Cobalt Radioisotopes; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005720:Gamma Rays; D006410:Hematopoiesis / Q000528:radiation effects*; D051379:Mice; D010315:Particle Accelerators; D011833:Radiation Injuries, Experimental / Q000401:mortality*; D012062:Relative Biological Effectiveness
chemical_list: D003037:Cobalt Radioisotopes