[Medical exposures based on the survey of the X-ray technical conditions and the proposal of guidance level].
The purpose of this work was to propose guidance levels of entrance surface doses for radiographic examinations of Japanese patients based on a nationwide survey. Questionnaires asking about the technical conditions of radiography were sent to 2,000 hospitals in Japan. The entrance doses (1st quartile, median, 3rd quartile, and mean) were calculated by the Numerical Dose Determination (NDD) method described in this paper and by using the conditions reported in the questionnaires. Our results for all types of examinations showed that the median was lower than the mean, whereas the median was higher than the mean in the results reported in the British NRPB 21. The median of our results was lower than that in the NRPB in England (Present work/NRPB in England = 0.27-0.74). We propose guidance levels of entrance surface doses for examinations carried out in Japanese institutions as the 3rd quartile of the dose distributions. The present proposed levels are lower than those described by IAEA. The calculated entrance surface doses exceeded the guidance levels set by IAEA in less than 10% of the institutions surveyed.