Nuclear medicine staff and patient doses in Manitoba (1981-1985)

The number of diagnostic in vivo nuclear medicine (NM) procedures in the Province of Manitoba (population 1 million) has been examined over the period 1981 to 1985. The annual number of procedures performed has remained relatively constant at about 25 per thousand population. The isotope 99mTc accounted for 86% of all the studies performed and the number of NM procedures per imaging system was approximately 1,300 per annum. The total number of NM operators in the province increased from 30 in 1981 to about 40 in 1985. The mean NM operator dose was reduced from 3.8 mSv to 2.5 mSv over this five-year period and the collective operator dose underwent a smaller reduction of 13% to about 100 person-mSv in 1985. The value of the mean patient effective dose equivalent (HE) was relatively constant at 5.2 mSv. The contribution of diagnostic NM procedures to the annual per caput population dose in Manitoba was 0.13 mSv. Three diagnostic procedures (brain, bone and cardiac) accounted for approximately 80% of the collective patient HE. Patient profiles (age, sex and medical history) were obtained for the patients undergoing these three procedures, which showed them to be atypical in comparison to a normal working population. These data suggested that the application of the International Commission on Radiological Protection risk factor of 1.65 X 10(-2) Sv-1 to this patient population would have significantly overestimated the expected radiation detriment.