Travelers who have recently undergone medical procedures that use radioactive drugs (search) may need a little extra preparation to clear security.

Radioactivity, such as from radioactive iodine (search) used in the treatment of thyroid disorders, can persist in an individual for weeks.

The radiation used in these types of treatments can trigger security radiation detectors, say researchers including Lionel Zuckier, MD, of the New Jersey Medical School.

The temporary trace of radiation that these therapies can leave in the body isn’t a public hazard. But according to Zuckier and colleagues, who presented their findings in Chicago at the Radiological Society of North America’s annual meeting, it might be enough to alert sensitive detectors.

Such devices are designed to catch smuggled radioactive material at U.S. borders and entry points.

Local, state, and federal officials have procured about 10,000 portable radiation detectors, according to a news release.

How long does the effect last?

Zuckier and colleagues tested the effects of different radiation treatments on the sensitivity of portable radiation detectors.

They found that one type of radioactive iodine therapy, frequently used in the treatment of thyroid cancer, set off portable detectors for up to 95 days. Heart imaging studies that use radioactive thallium (search) triggered detectors for about a month.

Other procedures had shorter effects.

Bone and thyroid scans, which frequently use lower and weaker doses of radiation, stopped setting off the detectors after about three days.

A doctor’s note could help answer any security questions. The card or letter should list the type of procedure, date, and a hospital contact person who can verify the treatment, according to a news release.

By Miranda Hitti, reviewed by Brunilda Nazario, MD

SOURCES: Radiological Society of North America 2004 Annual Meeting, Chicago, Nov. 28-Dec. 3, 2004. News release, Radiological Society of North America.