External radiation doses to nuclear medicine technologists from procedures using 99mTc radiopharmaceuticals.

In the course of their work Nuclear Medicine technologists are exposed to continuous low doses of ionising radiation, most of which is received during the use of 99mTc. This study investigated the radiation exposures received by technologists at a typical Canadian Nuclear Medicine department, during the most commonly performed 99mTC imaging procedures. Exposure rates were measured from both shielded and unshielded syringes containing typical amounts of injected radioactivity. Typical exposure rates received from patients were also measured during actual imaging procedures. From these measurements the cumulative absorbed doses per technologist, per annum, during radionuclide handling and patient imaging was calculated, for each of the procedures investigated. The results show that by far the greatest proportion of a Nuclear Medicine technologist's exposure is received during the imaging process rather than during radionuclide handling. Brain static, and bone, imaging provide the greatest exposures from patients. Cumulative doses can be considerably reduced by keeping technologist-patient distances to a maximum. The use of a lead apron would be most beneficial during close patient contact in bone and brain imaging procedures.