ESR News April 2016

Radiation incidents and accidents in radiology departments

John Damilakis, Professor of Medical Physics

 

Scientific literature shows the existence of a large variation of patient radiation doses in diagnostic and interventional x-ray examinations, mainly due to differences in examination protocols. However, there are radiation incidents involving the exposure of a patient to a dose much greater than intended. The main reasons for these very high doses are a) lack of knowledge in medical radiation protection, b) poor equipment knowledge and c) use of inappropriate protocols. There are also other causes of accidental exposure, such as the failure of staff to properly check the identity of patients. This may lead to radiation exposure of a patient who undergoes an x-ray procedure intended for another patient.

There are data on radiological incidents/accidents in the literature. A recent review paper provides information on radiation overexposure accidents worldwide (1). A well known accident occurred in 2009, when more than 250 patients in the USA received overdoses from brain perfusion CT. In some patients, deterministic effects (skin injuries and hair loss) were observed after the exposure. However, there are also radiation incidents where radiation doses are not high enough to produce deterministic effects. In these cases, the problem may go undetected.

The possibility of pregnancy should always be evaluated before an x-ray diagnostic or interventional procedure. Accidental irradiation of pregnant patients during the first post-conception weeks leads to unnecessary termination of pregnancies. To avoid these radiation accidents, proper pregnancy screening is needed. Referring physicians must check a box on the examination request form if the patient is pregnant. For abdominal procedures, thorough investigation of the reproductive status of young female patients is needed. It is very important to have pregnancy warning posters at the reception areas and patient waiting rooms

In fluoroscopically-guided interventional procedures with very long screening times, there is a possibility of cell killing sufficient to result in radiation-induced injuries in certain tissues of patients. Procedures typically involving extended fluoroscopic time include vascular embolisation, stent and filter placement, thrombolytic and fibrinolytic procedures, percutaneous transhepatic cholangiography, percutaneous nephrostomy, biliary drainage, percutaneous transluminal angioplasty and urinary/biliary stone removal. Interventional radiologists performing these procedures should be aware of the potential for injuries during these procedures. To avoid radiation overexposure accidents in interventional suites, interventional radiologists, in cooperation with medical physicists, should establish standard clinical protocols for each specific type of procedure performed. Cumulative absorbed dose to the skin should be limited to the minimum necessary for the clinical task. Medical physicists should perform detailed dose measurements to derive dose rates for each mode of operation used in each interventional system. Dose information should be included in the patient’s record to allow estimation of the absorbed dose to the skin in case of skin injury. It is important to note that radiation-induced lesions from fluoroscopic interventional procedures are not immediately visible because the radiation effects may appear several days, weeks or months following the exposure. Thus, patients sometimes are undiagnosed or misdiagnosed. For this reason, interventional radiologists should advise patients to provide information about their history of fluoroscopy exposure to the physician if they notice skin injuries.

Accidental medical exposure is a source of continuing concern. Article 63 of the new European Union Basic Safety Standards (2) focuses on accidental and unintended exposure. This article states that ‘Member States shall ensure that:

(a) all reasonable measures are taken to minimise the probability and magnitude of accidental or unintended exposures of individuals subject to medical exposure;

(b) for radiotherapeutic practices the quality assurance programme includes a study of the risk of accidental or unintended exposures;

(c) for all medical exposures the undertaking implements an appropriate system for the record keeping and analysis of events involving or potentially involving accidental or unintended medical exposures, commensurate with the radiological risk posed by the practice;

(d) arrangements are made to inform the referrer and the practitioner, and the patient, or their representative, about clinically significant unintended or accidental exposures and the results of the analysis;

(e) (i) the undertaking declares as soon as possible to the competent authority the occurrence of significant events as defined by the competent authority;

(ii) the results of the investigation and the corrective measures to avoid such events are reported to the competent authority within the time period specified by the Member State;

(f) mechanisms are in place for the timely dissemination of information, relevant to radiation protection in medical exposure, regarding lessons learned from significant events’.

 

References

  1. Coeytaux K et al, Reported radiation overexposure accidents worldwide, 1980-2013 : A systematic review. PLos One, Mar 19;10(3):e0118709, 2015
  2. Council of the European Union. (2013). Council Directive 2013/59/Euratom laying down basic safety standards for protection against the dangers arising from exposure to ionising radiation, and repealing Directives 89/618/Euratom, 90/641/Euratom, 96/29/Euratom, 97/43/Euratom and 2003/122/Euratom. Official Journal L-13 of 17.01.2014.