Population radiation dose from diagnostic nuclear medicine procedures in the Tehran population in 1999-2003: striking changes in only one decade.

Use of unsealed radiopharmaceuticals in Iran's nuclear medicine centers has expanded rapidly in the last decade. As part of a nationwide survey, this study was undertaken to estimate the radiation risk due to the diagnostic nuclear medicine procedures performed in Tehran in 1999-2003. During the five years of the study, the data of 101,540 yearly examinations of diagnostic nuclear medicine were obtained for 34 (out of 40) active nuclear medicine centers in Tehran. The patients studied were aged 1 y, 5 y, 10 y, 15 y, and adults (>15 y). Compared to an earlier investigation in 1989 (which was published in 1995), striking changes were found to be occurring in the trends of nuclear medicine in Tehran in a matter of a decade. The frequency of cardiac examinations increased from less than 1% in 1989 to 43.2% (mean of 5 y) in 2003; thyroid examinations, with the relative frequency of higher than 80% in 1989, decreased to 26.7% in the current investigation (averaged for 2001); and the number of overall examinations per 1,000 population of Tehran increased from 1.9 in 1989 to 8.8 in this study (about fourfold). The decrease in relative frequency of thyroid examinations could be attributed to the lower referral policy (mainly by specialists), decreased incidence of goiter due to implementation of programs for iodine enrichment diets, introduction of fine needle aspiration (FNA), and sonography techniques for diagnosis of thyroid disease. The large increase in relative frequency of cardiac examinations could be due to the increase in the number of single photon emission computerized tomography (SPECT) systems in recent years as compared to 1989 in Tehran. The collective effective dose increased from 400 (person-Sv) in 1999 to 529 (person-Sv) in 2003, and the effective dose per capita increased from 34.80 μSv in 1999 to 44.06 μSv in 2003 (average, 35.60 μSv).