RSNA News - December 2004

Radiologists Can Help Patients Avoid Triggering Security Detectors

We found that even miniscule amounts of radionuclides could set off the detectors.
— Lionel Zuckier, M.D.

After undergoing certain nuclear medicine procedures, patients can trigger radiation detectors for up to three months—something radiologists must discuss with their patients, according to a scientific paper presentation at RSNA 2004.

Lionel Zuckier, M.D., a professor of radiology at the University of Medicine and Dentistry of New Jersey, and colleagues found that patients who undergo exams, such as bone and thyroid scans, cardiac exams and iodine therapy, are at risk of setting off Homeland Security detectors for much longer periods than previously imagined.

"The nuclear medicine community has known for some time that these patients can set off radiation detectors. It's becoming a more common occurrence with the increasing number of very sensitive portable Homeland Security radiation detectors given to police officers, airport security personnel and border patrols," says Dr. Zuckier, who is also the director of nuclear medicine and PET at University Hospital in Newark.

He supports recommendations made by the Society of Nuclear Medicine (SNM) and the U.S. Nuclear Regulatory Commission (NRC) that radiologists and hospitals should provide official documentation to the more than 18-million patients who undergo nuclear medicine and therapeutic procedures each year. His study suggests guidelines as to how long this documentation should be retained.

Not a New Problem

Dr. Zuckier says initial reports of nuclear medicine patients setting off radiation detectors came almost two decades ago. A 1986 letter to the editor of The New England Journal of Medicine, "Problems on Pennsylvania Avenue," described how, in two separate incidents, nuclear medicine patients set off detectors at the White House.

More recently, the NRC has alerted users to an event where a patient who had undergone a nuclear medicine procedure ignored written safety instructions not to travel for two days. The patient boarded a bus traveling from New York City to Atlantic City. The bus was subsequently pulled over when a radiation alarm sounded in a tunnel. While there was no danger to those on the bus, this incident did cause unnecessary concern for travelers and law enforcement officials.

With today's state of heightened security, Dr. Zuckier and his colleagues wondered how long patients undergoing diagnostic and therapeutic nuclear medicine procedures could potentially set off detectors—such as those used by Homeland Security personnel. The researchers tested the sensitivity of a panel of detectors to various radionuclides and, making the assumption that personal radiation detectors worn by security officers could be positioned as close as one meter away from a patient, calculated the threshold of radionuclides that would trigger these devices.

In collaboration with Michael G. Stabin, Ph.D., from Vanderbilt University in Nashville, Tenn., who provided expertise regarding rates of excretion of radiopharmaceuticals from the body, the authors then calculated how long it would take for the patient to drop below the thresholds needed to trigger the alarms.

"In our experimental measurements, we found that even miniscule amounts of radionuclides could set off the detectors," says Dr. Zuckier. "Consequently, the length of time it took for the human body to excrete the radiopharmaceuticals to below threshold levels was much longer than expected."

What Should Radiologists Do?

SNM says radiologists can help patients and security personnel by providing patients who will be traveling on public transportation (such as airplanes, trains and rapid transit) or visiting secure facilities with a letter that contains the following information:

• Patient name
• Name and date of nuclear medicine procedure
• Radionuclide
• Half-life
• Administered activity
• 24-hour contact information

SNM says the letter should also provide specific details about who should be contacted, if necessary, for verification. Outside of normal working hours, the contact person should have access to an appropriate source of information such as a hospital or radiology information system, so that the letter can be independently confirmed.

While this is an extremely important matter, Dr. Zuckier says his study should not alarm the public nor should patients avoid needed procedures for fear of triggering radiation alarms. The amount of radiation a patient receives from a typical nuclear medicine procedure is minimal, but he says under the current climate of security consciousness, patients should be provided with a note from their doctors.

In addition to presenting the scientific paper at RSNA 2004, Dr. Zuckier also participated in an RSNA press conference in which he discussed his findings with the medical news media. To view the news releases from the annual meeting, go to rsna.org/press04.