Happens all the time (Score 2, Interesting)

Patients are given paperwork to prove that they have had nuclear medicine tests (what isotope and how much activity.) Nuclear power plant workers set off the detectors when they go back to work after Tl/Tc99m stress tests all the time down here in Fl. Longer lived isotopes like I131 for thyroid cancer ablation lasts quite a long time in the body (long biological half life with an 8 day half life.) All the major highways into NYC have detectors. Old news people...