The Effect of Dose-rate on the Acute Lethal Response of Dogs

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Abstract
The response of beagles exposed dorso-ventrally was determined for graded doses of 1000 kvp x-rays administered at 1 and 11·4 or 12·2 R/min. The estimated median lethal dose for the higher intensity exposure was 386 rads as compared with 524 rads after exposure at 1 R/min. The time of onset of the acute radiation syndrome, incidence and severity of pathophysiological responses, and length of survival of beagles were dependent on total dose delivered and exposure intensity. For doses producing comparable mortality the onset of illness was accelerated and the signs more pronounced at the higher exposure intensity. Death ensued earlier after higher intensity irradiation. Studies in the literature for wholebody irradiation of dogs are summarized. An empirical relationship of median lethal dose to exposure intensity is derived. A two-fold change in effective dose for lethality production was noted over the intensities used, and at an exposure intensity of 1 R/min the estimated LD50 for the dog was 421 rads.