Background: Hot lab is a specially designed room in a nuclear medicine hospital where the radiopharmaceuticals are delivered, stored and prepared for dispensing. ⁹⁹Mo/^99mTc-generator is the major source in the hot lab used for various medical imaging. It is important to maintain a standard for hot lab procedures to optimize the patient care and minimize radiation exposure to all nuclear medicine personnel, patients, public, as well as environment.

Materials and Methods: The radiation doses in the hot lab were measured by GM and NaI Detectors for about 12 months. Package surface doses and generator surface doses were also measured. An increase in the counted rate above background was considered for the study. A constant distance was made in every step.

Results: At the receipt date, the ⁹⁹Mo/^99mTc-generator surface dose (450±150 μGy/hr) found to be nearly six times higher than the package surface dose (80±20 μGy/hr). The dose rate at the outer surface of the fume-hood glass found to be 80±15 μGy/hr in the 1^st day of generator
placement, whereas at the 2^nd day it was 70±12 μGy/hr; showing a gradual decline in dose rate during 3^rd (50±10 μGy/hr), 4^th (40±9 μGy/hr), 5^th day (30±6 μGy/hr) and 6^th day (25±4 μGy/hr).

Conclusion: In the 1^st day of a generator storing in the hot lab, the dose rate found to be 3-4 times higher than the 6^th days. The dose rate at various places indicated poor performance of the fume-hood glass. The study emphasizes on the need of growing awareness among all the
radiation workers and encouraging the safe working practices in nuclear medicine. Iran . J. Radiat. Res., 2004; 2 (2): 75-78