Initial experience with an 11 MeV self-shielded medical cyclotron on operation and radiation safety.

A self-shielded medical cyclotron (11 MeV) was commissioned at our center, to produce positron emitters, namely, (18)F, (15)O, (13)N and (11)C for positron emission tomography (PET) imaging. Presently the cyclotron has been exclusively used for the production of (18)F- for (18)F-FDG imaging. The operational parameters which influence the yield of (18)F- production were monitored. The radiation levels in the cyclotron and radiochemistry laboratory were also monitored to assess the radiation safety status in the facility. The target material, (18)O water, is bombarded with proton beam from the cyclotron to produce (18)F- ion that is used for the synthesis of (18)F-FDG. The operational parameters which influence the yield of (18)F- were observed during 292 production runs out of a total of more than 400 runs. The radiation dose levels were also measured in the facility at various locations during cyclotron production runs and in the radiochemistry laboratory during (18)F-FDG syntheses. It was observed that rinsing the target after delivery increased the number of production runs in a given target, as well as resulted in a better correlation between the duration of bombardment and the end of bombardment (18)F- activity with absolutely clean target after being rebuilt. The radiation levels in the cyclotron and radiochemistry laboratory were observed to be well within prescribed limits with safe work practice.