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Q & A: gamma radiation safety

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Most recent answer: 10/20/2015
Q:
I am a nuc med tech in a PET/CT department, and I cannot seem to find the answer for this. How far can the photons/gamma rays created by the positron/electron collision/annihilation travel once the FDG (18-F) is injected into the patient? I have been told as little as 5 feet, meaning if I stand 5 feet away from them, I am receiving no radiation. That does not seem correct?
- Stella
USA
A:

The 500keV gamma rays from these PET sources are not at all well screened by air. Distance from the source helps mainly because they spread out in all directions, so the dose falls off as the square of the distance from the source. There's no single magic distance in the room at which the dose falls off rapidly.

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Mike W.


(published on 10/20/2015)

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