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Iodine Treatments Can Set Off Security Alarms

Effect seen if traveling up to three months after therapy for thyroid disorders

WEDNESDAY, Dec. 1, 2004 (HealthDayNews) -- People who have had iodine treatment for thyroid disorders can trigger homeland-security alarms for up to three months following their therapy, new research shows.

Other diagnostic nuclear medicine procedures such as PET, bone and cardiac scans can also set off the devices, although for shorter periods of time after treatment.

While the alarm problem has always been a small risk for individuals undergoing one of these procedures, it is becoming more commonplace with 10,000 portable radiation detectors now assigned to state, local and federal officials around the United States. This is in addition to permanent detectors present at assorted locations.

An estimated 18.4 million nuclear medicine imaging and therapeutic procedures were performed in 2002 in the United States. The amounts of radiation used are not harmful.

"These are trace amounts but the detectors are extremely sensitive," explained study author Dr. Lionel Zuckier, a professor of radiology at New Jersey Medical School University of Medicine and Dentistry of New Jersey, and director of nuclear medicine and the PET program at University Hospital, both in Newark. "It's not surprising that, with the frequency of procedures and the number of detectors, many patients have been picked up by these detectors and detained until their status can be clarified."

Zuckier presented his findings Nov. 30 at the Radiological Society of North America annual meeting in Chicago.

The Society of Nuclear Medicine (SNM) and the U.S. Nuclear Regulatory Commission (NRC) recommend that people who have undergone one of these procedures carry a letter detailing the procedure and listing who can be contacted to confirm the service. The question is how long do patients need to carry this paperwork.

"These recommendations beg the question, how long should these pieces of paper be carried on the patient?" Zuckier said. "That's where our study came in."

Zuckier and his colleagues looked at five personal radiation detectors and measured the levels of seven commonly used radionuclides (Tl-201, Tc-99m, Ga-67, I-123, In-111, I-131, F-18) that would set them off and at what distance.

Iodine therapy (I-131), used to treat thyroid cancer and other conditions, lasted 95 to 100 days. "To me, that's not so surprising because this has a long half-life and is given in a large amount for therapy," Zuckier said.

Cardiac exams with thallium lasted up to 30 days; bone and thyroid scans with Tc-99m up to three days, and FDG PET scans less than 24 hours.

Zuckier recommends that individuals carry paperwork with them for the maximum amount of time they could be setting off security alarms. That way they might avoid the fate of a man who boarded a bus to Atlantic City, N.J., and triggered an alarm in one of the tunnels leading out of New York City after being treated with radionuclides.

"We suggest that physicians follow the recommendations of the SNM and the NRC and provide patients with written documentation regarding the procedure for the period we have calculated," he said.

As for the man headed to Atlantic City, he was eventually exonerated --but not before the bus was stopped and searched. "It was a huge inconvenience to passengers and the security services," Zuckier said. Still, he added, "compared to the benefit [radionuclides] provide to patients, it's more of a nuisance."

More information

Visit the Society of Nuclear Medicine for more on this type of procedure.

SOURCES: Nov. 30, 2004, news conference with Lionel Zuckier, M.D., professor, radiology, New Jersey Medical School University of Medicine and Dentistry of New Jersey, and director, nuclear medicine and the PET program, University Hospital, both in Newark
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