People undergoing scans involving radioisotopes beware: you might set off airport security radiation alarms for as long as a month after the procedure.

That's the conclusion reached by the authors of a case report in the current issue of The Lancet.

Lead researcher Richard Underwood of London's Royal Brompton Hospital and his team members are calling for patients to be issued an information card after procedures involving radioisotopes.

"Stricter measure, and more sensitive radiation detection systems, are being deployed at airports worldwide," said Underwood. "It is important to warn patients having had a thallium scan that they might trigger radiation detectors for up to 30 days."

He said such patients should be given an information card stating the date and place of the procedure; the radioisotope used and its half-life; potential duration of radioactive emissions from the patient; and details on whom to contact for verification, if necessary.

Such information cards, he said, might lessen the impact of such false alarms and avoid unnecessary interrogations by airport security personnel.

Copyright 2005 by United Press International