[Relative biological efficiency of electron and photons of a 42-MeV- betatron. LD 50/30 in mice].

The LD 50/30d in young NMRI mice was determined. Comparison was made for 200 kVp X-rays, Cobalt-60 gamma rays, 35 MeV electrons and 42 MV bremsstrahlung. The dose rate was in all experiments between 60 and 80 rd per minute. The beam geometry and the spatial dose distributions were held as equal as possible. With 200 kVp X-rays as unity the same RBE factor (0.80 plus or minus 0.05) resulted for Cobalt-60 gamma rays, 35 MeV electrons and 42 MV bremsstrahlung.