Radionuclides trip portable security detectors

Nuclear medicine physicians should take not only a patient's history, but also his or her "future." Patients who travel after a diagnostic or therapeutic nuclear medicine procedure can accidentally trip alarms designed to catch terrorists smuggling radioactive material.

Patients can trigger radiation detectors up to three months after the administration of some nuclear therapies, according to a study presented at the 2004 RSNA meeting.

Dr. Lionel Zuckier and colleagues at the New Jersey University School of Medicine and Dentistry assessed the potential duration of radionuclides in the body by analyzing their sensitivity to detectors used by the Department of Homeland Security.

Using five different portable detectors, the researchers tested seven substances: thallium-201, technetium-99m, gallium-67, iodine-123, iodine-131, indium-111, and F-18 FDG.

They found that I-131 (including Bexxar, the non-Hodgkin's lymphoma treatment) may trigger an alarm up to 95 days postadministration. Detectable traces of the other radionuclides remain in the system for varying lengths of time:

• up to 30 days: Ga-67 and Tl-201

• up to 17 days: In-111

• up to three days: Tc-99m and I-123

• less than 24 hours: F-18 FDG

All five detectors in the experiment exhibited similar sensitivity.

While this is not a new problem (in 1986 two nuclear medicine patients set off detectors in the White House), it may become a more commonplace occurrence as portable radiation monitors proliferate and the number of nuclear medicine scans increases, said Zuckier, a professor of radiology at the New Jersey university.

The number of portable devices in use in the U.S. could be as high as 10,000, according to DHS figures. The number of diagnostic and therapeutic nuclear medicine procedures in 2002 was close to 20 million and increasing nearly 10% annually, according to figures from the Society of Nuclear Medicine.

One man a few years ago set off an alarm in a tunnel while on a bus ride from New York to Atlantic City. He had ignored warnings from his physician regarding travel restrictions.

The SNM recommends that physicians give patients a letter detailing the procedure and its date, the radionuclide and its half-life, and 24-hour contact information.

For more information from the Diagnostic Imaging archives:

Federal agency adds x-rays to carcinogen warning list

Bioluminescent light shines on MI