title: Relative biological effectiveness measurements using murine lethality and survival of intestinal and hematopoietic stem cells after fermilab neutrons compared to JANUS reactor neutrons and 60Co gamma rays.
abstract: The relative biological effectiveness (RBE) of the 25-MeV (average energy) neutron beam at the Fermi National Accelerator Laboratory was measured using murine bone marrow (LD50/30) and gut (LD50/6) lethality and killing of hematopoietic colony forming units (CFU-S) or intestinal clonogenic cells (ICC). The reference radiation was 60Co gamma rays. The LD50/30 and LD50/6 for mice exposed to the Fermilab neutron beam were 6.6 and 8.7 Gy, respectively, intermediate between those of JANUS neutrons and 60Co gamma rays. The D0 values for CFU-S and ICC were 47 cGy and 1.05 Gy, respectively, also intermediate between the lowest values found for JANUS neutrons and the highest values found after 60Co gamma rays. The split-dose survival ratios for CFU-S at intervals of 1-6 hr between doses were essentially 1.0 for both neutron sources, while the corresponding split-dose survival ratio for 60Co gamma rays was consistantly above 1, reaching a maximum of 1.7 with a 1-hr interval between doses. The 3-hr split-dose survival ratios for ICC were 1.0 for JANUS neutrons, 1.85 for Fermilab neutrons, and 6.5 for 60Co gamma rays. The RBE estimates for LD50/30 were 1.5 and 2.3 for Fermilab and JANUS neutrons, respectively. Based on LD50/6, the RBEs were 1.9 (Fermilab) and 3.0 (JANUS). The RBEs for CFU-S D0 were 1.4 (Fermilab) and 1.9 (JANUS) and for jejunal microcolony D0 1.4 (Fermilab) and 2.8 (JANUS).
mesh_terms: D000818:Animals; D003037:Cobalt Radioisotopes; D005214:Fast Neutrons; D005720:Gamma Rays; D006412:Hematopoietic Stem Cells / Q000528:radiation effects*; D007422:Intestines / Q000528:radiation effects*; D008297:Male; D051379:Mice; D009502:Neutrons; D009688:Nuclear Reactors; D010315:Particle Accelerators; D011833:Radiation Injuries, Experimental / Q000401:mortality*; D012062:Relative Biological Effectiveness
chemical_list: D003037:Cobalt Radioisotopes