The relative biological effectiveness of fast neutrons (42MeVd leads to Be) for early and late normal tissue injury in the pig.
Early and late radiation damage has been investigated in a number of normal tissues in the pig after irradiation with single doses of neutrons produced by 42MeV deuterons on beryllium. The results have been compared with data obtained after irradiation with single doses of 250kV X rays. In the skin a low RBE value of approximately 1.2 was obtained for the early (3-9 week) epithelial reaction. For the subsequent dermal vascular response, higher RBE values in the range of 1.35-1.6 were obtained: the RBE decreasing with an increase in the neutron dose. For late skin damage, assessed by the relative reduction in the linear dimensions of an irradiated field, a RBE value of approximately 1.5 was obtained. In the kidney the RBE value, for a neutron dose level (550 cGy) at which renal function was just preserved, was 2.0. A lower value of 1.7 was found for doses resulting in a loss of renal function. The results of 133Xenon clearance studies showed two waves of impaired ventilation function in the irradiated lung. In the acute reaction (3-9 months), at a dose level consistent with just preserving normal ventilation function, the RBE value was less than 1.2. For late lung damage (15-24 months) the RBE value was higher, 1.4. For the rectum, methods are presently only available for assessing acute damage. A RBE of 2.0 was found for neutron doses in the range 350-575 cGy. The RBE values for early endpoints in the skin, lung and gut of the pig are comparable with those published previously for other species, including man. The values for late effects in pig skin and lung were higher than for early damage in those tissues.
D000818:Animals; D004307:Dose-Response Relationship, Radiation; D005214:Fast Neutrons; D007668:Kidney / Q000528:radiation effects*; D008168:Lung / Q000528:radiation effects*; D009502:Neutrons; D012007:Rectum / Q000528:radiation effects*; D012062:Relative Biological Effectiveness; D012867:Skin / Q000528:radiation effects*; D013552:Swine; D013997:Time Factors; D014965:X-Rays