A person who has received a radionuclide for diagnosis or therapy may excrete the chemical for several days. This may be sufficient to trigger radiation alarms at airports, government offices or other sites.
Risk factors:
(1) type of radionuclide and its radiation half-life
(2) dose of the radionuclide
(3) amount of time between the dose and passing through a detector
Radionuclides that may trigger an alarm 1-3 days after exposure:
(1) fluoride 18 (1 day)
(2) iodine 123 (3 days)
(3) technetium 99m (3 days)
Radionuclides that may trigger an alarm 2 weeks after exposure:
(1) indium 111 (14 days)
Radionuclide that may trigger an alarm 1-3 months after exposure:
(1) gallium 67 (30 days)
(2) iodine 131 (95 days)
(3) thallium 201 (30 days)
Options for a traveler to reduce delays:
(1) delay travel until after excretion window has passed
(2) notify airport in advance
(3) obtain a notice from the physician documenting the exposure
(4) be screened for radioactivity (a low dose may clear more quickly)
It is important for the radiologist to notify patients of this risk, since otherwise they will be caught unaware. The handling of someone who sets off an alarm may not be pleasant.
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