This study estimates the length of time a patient might trigger security radiation detection devices after thallium 201 cardiac imaging. The US Department of Homeland Security is supporting the purchase and deployment of radiation detection pagers and portal monitors. Concurrently, there are an increasing number of cardiac perfusion imaging studies being performed using Tl-201. Therefore there is a higher probability that patients who have undergone nuclear medicine procedures could trigger alarms resulting in security questions.
METHODS AND RESULTS:
The length of time patients could trigger such devices is estimated based on the radiopharmacokinetics of Tl-201 and potential radioactive contaminants as well as the capabilities of current sensitive radiation detection devices, assuming the radioactive sources are distributed in and attenuated by the patient. It is estimated that patients may trigger portable pager devices for up to 33 days and may trigger portal detectors for up to 51 days after studies using Tl-201. This is much longer than length of time for a patient to trigger such alarms after technetium 99m myocardial imaging tests, which is potentially up to 6 days.
It should be standard practice for patients to be issued information cards that indicate the potential time for triggering security radiation detectors after diagnostic cardiac procedures involving the use of Tl-201 or other radiopharmaceuticals.
A 47-year-old man presented to the Emergency Department (ED) in duress and stated he was “highly radioactive.” There were no reports of nuclear disasters, spills, or mishaps in the local area.
This report discusses the potential for thallium-201 (Tl-201) patients to activate passive radiation alarms days to weeks after nuclear stress tests, even while shielded inside industrial vehicles away from sensors. Characteristics of Tl-201, as used for medical imaging, are described.
This patient was twice detained by Homeland Security Agents and searched after he activated radiation detectors at a seaport security checkpoint. Security agents deemed him not to be a threat, but they expressed concern regarding his health and level of personal radioactivity. The patient was subsequently barred from his job and sent to the hospital. Tl-201 is a widely used radioisotope for medical imaging. The radioactive half-life of Tl-201 is 73.1h, however, reported periods of extended personal radiation have been seen as far out as 61 days post-administration.
This case describes an anxious, but otherwise asymptomatic patient presenting to the ED with detection of low-level personal radiation. Documentation should be provided to and carried by individuals receiving radionuclides for a minimum of five to six half-lives of the longest-lasting isotope provided. Patients receiving Tl-201 should understand the potential for security issues; reducing probable tense moments, confusion, and anxiety to themselves, their employers, security officials, and ED staff.