[Cancinogenic effects of fast helium ions with energy of 4 GeV/nucleon in rats].

The study was made of carcinogenic efficiency of 4 GeV/nucleon helium ions (LET = 0.88 keV/um) in comparison with gamma-radiation 60Co (LET = 0.23 keV/um). Adult outbred female rats underwent a single whole-body irradiation with helium ions in doses 0.25-4.0 Gy at the Synchrophasotron of the Joint Institute for Nuclear Research and with gamma-rays at "PX-gamma-30" irradiator in doses ranged from 0.5 to 4.0 Gy. The yields, histology and occurrence time of hemoblastoses and tumours in mammary glands, in endocrine glands, in soft tissues and in other organs were determined. Histological study was made using conventional methods. The irradiation of experimental animals with accelerated helium ions and standard radiation was shown to result in an increase in the yield of growths of various localizations with decreasing occurrence time and expanding histological spectrum as compared with intact rats. However, helium ions possess a higher carcinogenic efficiency. The coefficients of relative biological effectiveness of helium ions calculated by the nonparametric method appeared to increase with decreasing the radiation dose.