Radiation detectors have been installed at UK ports and airports to screen vehicles and passengers for illegal radioactive substances on entry to the UK. The mobile and fixed detectors are being gradually introduced by HM Revenue and Customs as part of programme Cyclamen (http://www.security.homeoffice.gov.uk/counter-terrorism-strategy/border-security/cylclamen/ (sic)). Customs officers should be able to identify the radionuclide after detecting a radioactive patient and hence deal with them sensitively.
Patients frequently travel (back) into the UK following administration of medical radionuclides. There are about 10,000 patients receiving radioiodine therapy for thyrotoxicosis [1] and around 600,000 diagnostic imaging procedures [2] per year in the UK. These patients can trigger radiation security detectors with distressing consequences and delays. The table below shows anecdotal and documented reports of patients activating alarms.
Radiopharmaceutical |
Activity (MBq) |
Time after administration |
Location |
Reference |
|---|---|---|---|---|
| Tc-99m Tetrofosmin | 350 | 3 days | Driving to continent | Maidstone Hospital |
| In-111 white cells | 20 | 2 weeks | UK | HSE report 416 |
| Tl-201 | 80 | 2 days | UK/Moscow | Iqbal 2005 |
| Tl-201 | - | 9 days | Bank vault | Levin 1988 |
| Tl-201 | - | 4 days | The Whitehouse | Toltzis 1986 |
| I-131 MIBG | 7000 | 8 weeks | UK/Bulgaria | St Bartholomews |
| I-131 | 148 | 3½ weeks | Vienna airport | Sinzinger 2005 |
| I-131 | 400 | 6 weeks | Orlando airport | Gangopadhyay 2006 |
| I-131 | 400 | 5½ weeks | - | St Bartholomews |
| I-131 | 600/td> | 9 days | US airport | Harley St |
| I-131 | <30* | - | Moscow | HSE report 416 |
*retained activity on discharge
The period of time after administration of a radiopharmaceutical that a typical patient can trigger a detector is uncertain since the sensitivity of the detectors has, understandably, not been released. The model that Zuckier et al. provides is based on US homeland security detectors and gives some indication of the periods involved. (http://njms.umdnj.edu/departments/radiology/radalarmcalculator.cfm). The model predicts that a radioiodine patient could trigger a detector after 95 days and a bone scan patient after 3 days and this is consistent with the experience at Maidstone. It should be noted however that the period of detection may be somewhat longer than predicted by the model.
The HSE Research Report 416 'Information to accompany patients undergoing nuclear medicine procedures' has recently been published (http://www.hse.gov.uk/research/rrhtm/rr416.htm). Twenty (36 %) of the departments provided written information to radioisotope therapy patients specifically for customs officers and 7 % were aware of specific problems at borders. Although patients are frequently screened for travel abroad, the oral advice was, necessarily, ad-hoc and information for customs/police often relied on the standard 'yellow card'. Only 12 % of departments provided information following diagnostic procedures and two reported incidents. Formal guidance is lacking, in particular the period that patients must carry information is largely unspecified and a general understanding that even patients undergoing diagnostic tests can trigger alarms is needed. National advice is likely to become more important with the introduction of further detectors in the UK and abroad and is recommended in Research Report 416.
The Administration of Radioactive Substances Advisory Committee (ARSAC) is considering this issue and intends to provide advice in the near future to the medical community through its website. In the meantime, it may be sensible for all patients undergoing radionuclide therapy or diagnosis to carry a medical note when travelling abroad. Customs officers are aware of these patients, have received appropriate guidance and will treat patients sensitively, observing confidentially as appropriate.
References
1. Lazarus JH. Guidelines for the use of radioiodine in the management of hyperthyroidism: a summary. Prepared by the Radioiodine Audit Subcommittee of the Royal College of Physicians Committee on Diabetes and Endocrinology, and the Research Unit of the Royal College of Physicians. J R Coll Physicians Lond 1995; 29: 464-469.
2. Hart D and Wall BF. UK nuclear medicine survey 2003-2004. Nucl Med Commun 2005; 26: 937-946.
Peace R. Nuclear medicine patients and radiation detectors at UK ports and airports. HSE Radiation Protection News, May 2007.
Dr. Richard Peace RVI Unit, Newcastle upon Tyne. Tel: +44 (0)191-233-6161.
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