As I have explained previously, the purpose of a PET scan is to detect regions of increased metabolic activity in the body. Increased activity is potentially indicative of cancer. This activity is detected by injecting a hungry person with radioactive glucose (sugar). The person then rests for an hour, and since the person hasn't eaten in awhile the sugar goes straight to the hungriest cells (cancer, if present). The radioactivity concentrates there, and when the person is scanned after the hour of resting this concentrated radioactivity (if present) is mapped.
What I don't think I've discussed previously is, what happens to the radioactivity after the scan? Well, it decays and goes away. The type of radioactivity used in a PET scan has a very, very short half life, so short in fact that the clinic receives a shipment of radioactivity for the morning patients and a separate shipment for the afternoon patients. Said another way, a shipment received in the morning is no longer radioactive enough to be used in the afternoon patients.
But there are several hours between "morning" and "afternoon". Needless to say, I was curious about how radioactive (hot) I'd be just after a PET scan.
Lucky for me, we have a Geiger counter at my place of work. A Geiger counter is a little box the size of a car battery with a microphone-like wand attached to it by a cord. When turned on it works much like a metal detector, making rapid beeps when it detects radiation nearby and only occasional beeps in its absence. My friend Sam was all too eager to use the Geiger counter on me, approximately 2.5 hours after the radioactivity was injected in my arm for the PET scan. Fortunately Torey had his camera. (Don't mind my ridiculous walking posture. Apparently I don't walk normally when I know there's a camera on me.)
Radiant indeed! I suppose that for as much as I hate PET scans, they provide a nerd's delight. Some amazing technologies are intertwined to make cancer detection happen, radioactivity and all. Nerd salute to physics!