Abstract
Objective: The study details our work in managing radiation doses to our workers and comforters when dealing with 18F-FDG under the ALARA principle.

Methods: Pakistan's first PET-CT suite with on-site cyclotron was designed under the guidelines of AAPM Task Group Report #108 in 2009. Concrete, Perspex and lead were used as shielding materials to justify cost and space availability. The controlled areas were designed for permissible dose limit of =< 2 microSv/hr. The staff members who have direct contact with 18F-FDG are given thermolumiscence dosimeters to record their monthly wholebody and extremities doses.

Results: Once operational, the maximum prevailing exposure is =< 10 microSv/ hr in FDG Synthesis unit at 5 Ci. The prevailing exposure in the PET-CT Console and injection room is =< 2 microSv/ hr, Prescanning room =< 5 microSv/ hr, post scanning room =< 0.2 microSv/ hr; cyclotron vault surrounding is =< 0.1 microSv/ hr. Nursing staff, injecting and dispensing 18F-FDG are rotated once in a week to inject ten patients per day/week using lead shielding to cover syringe, lead bricks and movable trolley. A short interaction between the patients are the technologists reduces the technologist's dose to =< 0.6 mSv/ month (=< 17 mSv/month). Three radio-chemists produce up to 5 Ci radioactive 18F-FDG on a daily basis in an automated shielded synthesis unit. The average radiation dose for each radiochemist is =< 0.7 mSv/month (=< 27 mSv/month). Medical Physicists and cyclotron engineers receive =< 0.5 mSv/month (=< 10 mSv/month). The comforters receive =< 1.5 mSv/scan recorded by the electronic pocket dosimeter (EPD). Each patient is released when the radiation exposure is reduced to =< 20 microSv/hr at 1 meter.

Conclusion: In the last five years (2009 to 2013), 10,000 patients were scanned with an average of 330 MBq injected dose. The maximum average dose received was 4 mSv/year for some members of nursing staff and radiochemists, whereas the least average dose of 1 mSv/year was received by technologists and the rest of the staff received doses =< 1 mSv/ year.