BMJ  2006;333:293-294 (5 August), doi:10.1136/bmj.333.7562.293

Practice

Lesson of the week

Triggering radiation alarms after radioiodine treatment

¹ Department of Medicine, Diabetes, and Endocrinology, City Hospital, Birmingham B18 7QH, ² Department of Nuclear Medicine, City Hospital, Birmingham

Increasing numbers of diagnostic and therapeutic procedures involving radioisotopes are being conducted. The most common procedures include thallium scans for myocardial perfusion, ventilation perfusion lung scans, bone scans, iodine uptake scans, and radioactive iodine as treatment for thyroid disorders. For thyrotoxicosis, for example, 10 000 patients received radioactive iodine (¹³¹I) treatment in one year in the United Kingdom alone.¹

Such procedures make patients temporarily radioactive and can be an important cause of false alarms at airports by activating radiation detectors. Doctors show a worrying lack of awareness about such potential problems. As a result, patients receiving radioactive isotopes for diagnostic and therapeutic purposes are not adequately warned about persisting radioactivity and precautions that need to be taken.² We report a case that further highlights this problem.

Case report

A 46 year old man was referred to our endocrine clinic in July 2003 with a history of weight loss, sweating, and diarrhoea. On examination he was sweaty and had a fine tremor. His pulse rate was 96 beats/min. He had no goitre. Investigations showed a free T4 of 93 pmol/l (range 10-24 pmol/l), free T3 of 30 pmol/l (3.5-6.5 pmol/l), and suppressed thyroid stimulating hormone(0.02 mU/l (0.5-5.0 mU/l)). He was treated with carbimazole 30 mg daily, which resulted in improvement of his symptoms. The dose of carbimazole was gradually reduced to 5 mg daily. However, his thyrotoxicosis relapsed in July 2004, and he was treated again with 30 mg carbimazole. Once he became euthyroid, radioiodine treatment was planned in view of recurrent thyrotoxicosis. In early December 2004 he was given 400 MBq of ¹³¹I. Our nuclear medicine department gave him the radionuclide instruction card highlighting the usual precautions to be taken. However, the card did not mention the risk of radiation detectors being triggered.

Six weeks later he went to the United States for a holiday. At Orlando airport he set off the security alarm at check-in. He was immediately detained and strip-searched. Sniffer dogs were also used. A prolonged period of interrogation ensued. Luckily, he was carrying his radionuclide card with him. He was finally released after a long delay and much embarrassment. While narrating this story in clinic, he stated that he would not have made the US journey if he had had any inkling of the harassment he was likely to face. We apologised to him for the lack of information given to him after the radioiodine treatment, and since this event changes have been made to the radionuclide card issued to patients.

Credit: JOHN POWELL/REX

 

Discussion

Given the current political climate, airport authorities are keen to detect any radioactive material being carried, and thus it is not surprising that anybody setting off radioactive alarms will be subjected to an extensive search and questioning. Unfortunately, this potential problem has not been adequately communicated to our patients, and unawareness persists even in some members of staff in nuclear medicine.² A literature search found only four case reports,^2-5 and this further highlights the problem.

In the first report (1986), two patients tried to enter the White House for a public tour four days after exercise stress testing with a thallium scan. They set off the radiation alarm and were detained till the cause of the security breach was established.³

In 1988, the day after having a thallium stress test, a 65 year old patient went to his bank to examine the contents of his safety box. The security alarm sounded when he entered the bank vault. He continued to set off the alarm on subsequent visits to the vault until the ninth day after his thallium stress test.⁴

In 2004, 25 days after having been treated with 150 MBq of radioiodine for toxic multinodular goitre, a 76 year old man set off the radiation alarm at Vienna international airport and was investigated thoroughly. After this, a radiation protection certificate was designed and given to patients receiving radionuclide treatment in Vienna, so that similar problems could be avoided.²

In 2004, two days after having a thallium-201 (²⁰¹TI) myocardial perfusion scan, a 55 year old pilot triggered the radiation detector alarms while travelling as a crew member to Moscow. After extensive investigations, he was released later that day. Four days later he set off the security alarm again at the same airport and was again detained but later released. He was then given a card by airport security that explained that the thallium scan was likely to set off alarms.⁵

When Zuckier et al studied the sensitivity of some security radiation detectors, they found that after receiving radioisotopes, patients might trigger radiation alarms for up to a varying number of days depending on the radioisotope.⁶ The table shows that patients receiving ¹³¹I, for example, may trigger the alarm for a substantial period of time (up to 95 days) because of the long half life of the isotope.⁶

View this table: [in this window] [in a new window]   Number of days up to which patients might trigger radiation alarms after receiving radioisotopes

 

Since the case of our patient described above, our nuclear medicine department has added the following statement to the radionuclide card given to patients: "Airport alarms may be triggered for up to 12 weeks after receiving your therapy dose."

Airports worldwide are deploying more sensitive radiation detection systems, and one would therefore expect more such cases unless we take the responsibility of forewarning our patients. Hence, we felt that it was important to dissipate this information in the hope that this will prevent further unnecessary harassment and embarrassment to patients.

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Editorial by Cuthbertson and Davidson

Patients receiving radioactive isotopes should be warned that they may trigger radiation alarms

Contributors: PD was the consultant in charge of the case, and is the guarantor for the article. All authors jointly managed the case. KKG did the literature search, wrote the first draft of the paper, and gained consent from the patient for publication. FS and PD made additions and corrections to the paper.

Competing interest: None declared.

References

1. Lazarus JH. Guidelines for the use of radioiodine in the management of hyperthyroidism: a summary. J R Coll Physicians Lond 1995;29:6: 464-9.[ISI][Medline]
2. Sinzinger H, Aiginger P, Neumann I, Havlik E. Radiation alarm at an airport after radioiodine therapy. Nucl Med Commun 2005;26(1): 67-8.[CrossRef][ISI][Medline]
3. Toltzis RJ, Morton DJ, Gerson MC. Problems on Pennysylvania Avenue. N Engl J Med 1986;315: 836-7.[ISI][Medline]
4. Levin ME, Fischer KC. Thallium stress tests and bank vaults. N Engl J Med 1988;315: 587.
5. Iqbal MB, Sharma R, Underwood SR, Kaddoura S. Radioisotopes and airport security. Lancet 2005;366: 342.[CrossRef][ISI][Medline]
6. Zuckier L, Stabin M, Garabeno G, Monetti M, Lanka V. Sensitivity of personal homeland security radiation detectors to medical radionuclides and implications for counseling of nuclear medicine patients. Radiological Society of North America (RSNA), 2004 (Abstract) http://rsna2004.rsna.org/rsna2004/V2004/conference/event_display.cfm?em_id=4407767 (accessed 7 Jun 2006).

(Accepted 7 March 2006)

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