Safety and PET / CT

We had a bit of a demo with a geiger counter to illustrate the importance of distance to maintaining staff safety when using PET. You probably remember that the annihilation photons are emmitted at 511KeV. With the geiger measuring background radiation at 18 counts per second the count a couple of feet from the patient was over 600 counts per second (one hour after the initial injection). So minimising time with the patient and maximising distance are all important. After learning to get close to patients this feels very odd !