title: RBE of neutrons generated by 50 MeV deuterons on beryllium for control of artificial pulmonary metastases of a mouse fibrosarcoma.
abstract: Artificial pulmonary metastases of a mouse fibrosarcoma were produced by the intravenous injection of 10(4) cells admixed with 2 X 10(6) plastic microspheres into mice preconditioned with 600 rad whole-body irradiation 24 hours earlier. Four days after injection of tumour cells, mice were irradiated with neutrons generated by 50 MeV deuterons on Be at the Texas A & M Variable Energy Cyclotron or with 137Cs gamma rays. One, three or six fractions of radiation were delivered on a three-hour fractionation schedule. Surviving lung metastases were scored macroscopically 16 days after irradiation. The data indicate that: (1) the RBE (n/gamma) was in the range 1.6-2.6 depending on the size of dose per fraction; (2) the slopes of the gamma-ray curves decreased with increasing fraction number (i.e. decreasing fraction size); (3) the slopes of the neutron curves decreased only slightly with increasing fraction number (and decreasing fraction size); (4) no additional sparing was achieved by further fractionating doses of neutrons of 300 rad or less.
mesh_terms: D000818:Animals; D002470:Cell Survival / Q000528:radiation effects; D003903:Deuterium; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005354:Fibrosarcoma / Q000532:radiotherapy*; D008175:Lung Neoplasms / Q000532:radiotherapy*; D051379:Mice; D009362:Neoplasm Metastasis; D009374:Neoplasms, Experimental / Q000532:radiotherapy; D009502:Neutrons; D012062:Relative Biological Effectiveness
chemical_list: D003903:Deuterium