[Studies about the exposure to radiation of the fetus in case of X-ray examination during gravidity (author's transl)].

In the second communication (Strahlentherapie 156 (1980), 776-785), we discussed the estimation of the exposure to radiation of the fetus by means of tube related data (product of area/surface dose or time/tube current). In this final communication, we present method and problems of the estimation based on the sensitivity of the picture-producing system. In order to apply this method, one must know several factors characterizing the attenuation of X-radiation between the point of incidence and the picture carrier. A detailed report is given on the results of measurements effected on a water phantom in order to find out these factors of attenuation. Then the estimated surface doses are compared to the values determined by thermoluminescence dosimetry. We come to the conclusion that the estimation of the exposure to radiation by means of tube related data will generally involve a lower deviation from the actual value than the estimation based on the dose required by the receiving system.