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The Biological Effect of Roentgen Rays of Long and Short Wavelength on the Totally Irradiated Rat

1941; Radiological Society of North America; Volume: 37; Issue: 6 Linguagem: Inglês

10.1148/37.6.724

1527-1315

J. Craig Potter,

Effects of Radiation Exposure

The purpose of this study was to compare the biological effects of three x-ray wavelengths on the totally irradiated rat. The lethal dose was used as the basis for comparison. At the same time, the result of irradiating the ovaries was studied by observing the fertility of the rats in the non-lethal experiments. The biological effect of different wavelengths has been investigated by Packard (1), using fruit fly eggs; by Quimby (2), with erythema doses on the skin; and by Harvey, Dresser, and Warren (3), who studied the sterilizing effect of different wavelengths on rabbit tumors. In general, all found the effects of different wavelengths to be the same. In none of these studies, however, with the possible exception of the work of Harvey, Dresser, and Warren on testicular tumors, was penetration a factor. In irradiation of the whole rat penetration becomes a factor, and the findings in this paper therefore add new observations. Whole rats were irradiated with heavily filtered rays at 400 kv., lightly filtered rays at 100 kv., and unfiltered rays at 100 kv. The doses were increased in different groups of rats 200 r units at a time until death resulted. Animals not destroyed were mated after five weeks to observe the effect on fertility. The rats were virgin females about two months old, each weighing approximately 150 gm. This study was continued over a period of eight years and nearly 500 rats were irradiated. The results obtained with the last 49 consecutive animals have been tabulated. The x-rays were generated by two machines. One was a 100-kv. generator with single valve rectification; the other was a 400-kv. machine with full-rectification, Villard circuit and Thoraeus A filter (0.6 mm. Sn + 1.5 mm. Cu + 1.0 mm. AI). The target skin distance was 80 em. in all. An effort was made to keep the time of irradiation the same for the different wavelengths. The r units were measured in air by means of a Victoreen r meter. With filtered radiation an entrance dose of 800 r at both 100 kv. and 400 kv. caused death. The animals died in a few days of enteritis. With unfiltered radiation at 100 kv., a 1,200 r entrance dose caused death in a week, as above. With a 1,000 r entrance dose of unfiltered radiation the animals lost weight and died in two to four weeks. Fertility continued, with all wavelengths, up to a dose which caused death. As the lethal entrance dose of unfiltered and filtered waves was not the same, the exit dose was determined to see if it offered a better means of comparison. This was computed by means of a paraffin phantom, 3.5 em. thick, and a paper box, 3.5 em. thick, in which 5 rats were tightly packed. At 400 kv. the exit measurement was three-fourths of the entrance measurement; at 100 kv, filtered, it was threefourths of the entrance measurement; at 100 kv., unfiltered, it was half the entrance measurement. The exit measurement which will kill all rats in a week is constant in the wavelengths studied.