About two years ago my wife had some radiation therapy. About a month afterward we travelled to Switzerland, transiting CDG. Nothing happened until we returned to IAH.

A very polite CBP officer at the exit (with a beeper of some kind going off) asked "Excuse me, did either of you recently have a medical procedure?". My wife says "Yes", and he says "Welcome home and I hope everything is OK". It wasn't until we had exited that we discussed the matter and realized what must have happened.

So we got out of the US, through French and Swiss airports, and not until we get home do they realize we have higher than normal radiation? That is the scary part, not being asked politely about a condition that obviously caused an alarm. I can live with that, especially after watching the current season of 24!