Effective radiation dose to the patient and to the general population from nuclear medicine procedures: variations in the last twenty-year period.

We have evaluated how changes in nuclear medicine (NM) techniques over the last twenty-year period have modified radiation exposure to the patient and population. For this purpose, we estimated the variations in the mean effective dose to the patient, and both the collective and the per capita effective dose to the population of the province of Varese, derived from radioisotope examinations carried out in the four NM Centers of this province in the years 1972, 1981, and 1991. Dosimetric calculations were based on ICRP Publication 53 for most of the radiopharmaceuticals used, and tissue weighting factors were based on ICRP Publication 60. The total number of NM exams carried out was 19,744 in 1972, 31,973 in 1981, and 23,623 in 1991. Between 1972 and 1991 there has been a substantial decrease in the effective irradiation to the patient and to the general population (mean effective dose to the patient: from 21.2 to 6 mSv; per capita mean effective dose: from 0.58 to 0.18 mSv), and in the per capita equivalent dose to some target organs, such as the thyroid (9.6-->1.5 mSv) and liver (0.51-->0.07 mSv). At the same time, there has been a significant increase in the per capita equivalent dose to the bladder (0.05-->0.48 mSv), skeleton (0.08-->0.36 mSv), and testes (0.02-->0.15 mSv), and a less marked increase to the ovaries (0.03-->0.06 mSv). The per capita equivalent dose to red marrow (0.13-->0.1 mSv) and to the large intestine (0.1-->0.12 mSv) did not change significantly.