Background and purpose: In recent years the use of radioactive materials for diagnostic and therapeutic purposes grew rapidly in nuclear medicine. The imaging technicians and nursing staff in radiopharmaceutical centers are in close contact with patients. Therefore, they are exposed to different radiation levels. This study was done on risk assessment of staff exposed to ^99mTc-MIBI

Materials and methods: In this study, the radiation dose rate from two groups of patients (rest patients n= 27 and rest patients n= 23) who received ^99mTc-MIBI for myocardial perfusion imaging was measured using detection at different distances in Shahrood Imam Hospital, Iran. Then, the radiation dose rate of the staff was calculated based on the duration of time they were exposed to radiation at different distances. 

Results: The value of radiation dose rate from patients receiving ^99mTc-MIBI for stress and rest patients were 9.9 and 13.4 micro Sv per hour in 25 cm distance from patients, respectively. By calculating the mean time of technicians’ close contact (less than a meter) with patients, their mean daily exposure rate was found to be 2.1±1.2 and 2.9±1.2 micro Sv per hour for rest and stress patients, respectively.

Conclusion: Compared with threshold level (60 micro Sv per day) lower levels of radiation exposure was seen in our population. But generally, the exposure rate in rest patients was found to be higher.