THE BURDEN TO THE SURFACE IN ROTATIONAL IRRADIATION WITH RADIATION OF 100 kev TO 100 Mev

The problem of the influence of radiation energy on the relative depth dose obtained by using rotational irradiation was investigated for radiations of 100 kev (normal radiation) to 17-Mev-x-ray radiation using uniform conditions. The diameters of the phantoms used varied between l2 and 30 cm and the field sizes between 3 and 7 cm. Because of the properties of high energy radiation, that is, greater relative depth dose, built-up effect, and less scattering, decreasing skin burdening results from increasing radiation energy related to the same focal doses. The requirement of keeping the skin dose three times smaller than the tocal dose can be already accomplished with the conventional radiation for small fields in case of rotational irradiation. In case of larger fields, harder radiation, for example Co/sup 60/ gamma rays or even better ultrahard radiation, is necessary, The use of radiation energies higher than about 10 to 20 Mev is not necessary and in certain cases even unprofitable. (auth)