DETERMINATIONS OF ORGAN OR TISSUE DOSES AND COLLECTIVE EFFECTIVE DOSE EQUIVALENT FROM DIAGNOSTIC-X-RAY EXAMINATIONS IN JAPAN

The frequency of diagnostic X ray examinations in Japan has been evaluated on the basis of the nationwide surveys of radiological examinations throughout the whole of Japan. For the determinations of organ or tissue doses, the technical factors for the radiological examinations were also investigated by the nationwide surveys. As an example of the results, the annual number of radiographs in 1986 totalled 497 million and the annual frequency of radiographic examinations was 141.5 million. The average number of the radiographs per examination was estimated to be about 3.5. The annual number of X ray CT examinations in 1989 was estimated to be 12 million. The resultant collective dose equivalent from X ray diagnosis including X ray CT was estimated to be about 2.4 x 10(5) person.Sv using organ or tissue doses determined with phantom measurements and the ICRP 1977 recommendation.