Are MIBI/tetrofosmin heart studies a potential radiation hazard to technologists?

The number of nuclear medicine studies is increasing and they are becoming more complex and time-consuming. In particular, this is true of myocardial perfusion investigations. We use a one-day protocol for these studies, utilizing Tc-99(m)-MIBI or Tc-99(m)-tetrofosmin with tomographic rest images (250 MBq) acquired in the morning and exercise images (750 MBq) approximately 4h later after pharmacological stress. Imaging technologists are concerned about continual exposure to 1000 MBq Tc-99(m) per study. Radiation doses were measured during rest (1.0 mu Sv, n = 18), exercise (2.5 mu Sv, n = 18) and stress administration (2.0 mu Sv, n = 16), giving a total dose of 5.5 mu Sv per combined cardiac study. We have previously shown that the average dose per radionuclide study (excluding myocardial perfusion studies) is 1.5 mu Sv. Although 5.5 mu Sv is higher, a technologist is highly unlikely to exceed current dose limits. New EC legislation, however, is expected to reduce these Limits, which may lead to more classified workers. Pregnant technologists should avoid, if possible, combined cardiac studies, especially if performing other nuclear medicine duties.