Accidental Doses in Dental Radiography

All employers must take steps to reduce the likelihood of anyone, whether staff or patients, receiving an accidental radiation dose due to their work with X-rays. Again we will look at this topic in two separate parts, for people at work, and then for patients. Note that an accident could lead to both staff and patients receiving doses that are higher than usual.

Accidental Doses to People Working with X-rays

As we saw in step 1.9, radiation doses must be restricted so far as is reasonably practicable and must not exceed the dose limits specified in the regulations. If it is suspected that a member of staff may have been unintentionally or accidentally exposed to radiation then you must:

• Follow the contingency plan given in the local rules
• Seek the advice of the RPA
• Determine the circumstances of the exposure
• Take any potentially faulty equipment out of use if the accidental exposure was due to an equipment fault
• If the person involved wears a personal dosemeter, this should be sent to the dosimetry service for immediate assessment; if not, the RPA should be asked to assist in estimating the magnitude of the dose received

What should happen next depends on the magnitude of the dose received.

a) Dose greater than the dose investigation level

IRR17 requires the employer to set an appropriate Dose Investigation Level (DIL). The DIL is intended to help the employer ensure that doses received by people working at the practice are being kept ALARP. A typical DIL for a dental practice is a total effective dose of 1 mSv per calendar year, but each employer should seek advice from their RPA about setting a suitable DIL for their practice.

If it is known or suspected that anyone has received a dose in a calendar year that exceeds the DIL, an investigation into the circumstances should be carried out in consultation with the RPA. The outcome of the investigation should set out any steps necessary in order to prevent a reoccurrence. A report of the investigation must be written and kept for two years.

b) Dose greater than the dose limit

Radiation doses to employees using dental X-ray equipment are normally very low, so it is unlikely that anyone will receive a dose above the dose limit, which is known as overexposure. However, it could be a possibility in the event of a serious equipment malfunction or if someone deliberately misused the equipment.

If you know or suspect that someone working with X-ray equipment at your practice has received an overexposure, you must notify the regulator. In the UK, this would be the HSE or the HSE(NI).

Accidental or Unintended Doses to Patients

The most likely causes of a patient receiving an accidental or unintended radiation exposure are equipment failure or operator error. IRMER17 requires the employer to put a procedure in place to minimise the chance of this happening; and a procedure to follow in the event of an incident occurring. These will be discussed in more detail in Week 4 of the course.

If it is suspected that a patient has received an accidental or unintended radiation dose, an immediate investigation should be carried out, in accordance with the relevant employer’s procedure. You should always seek advice from your MPE. Patient exposures that are suspected of being ‘significant accidental or unintended exposures’ (SAUE) or ‘clinically significant accidental or unintended exposures’ (CSAUE) must be reported to the regulator. A list of regulators for different parts of the UK is given below:

England: The Care Quality Commission

Wales: Healthcare Inspectorate Wales

Northern Ireland: The Regulation and Quality Improvement Authority

Scotland: Healthcare Improvement Scotland

As the above authorities have different criteria for the types and magnitude of exposures that must be reported, you should consult your MPE who will advise you if the accidental or unintended exposure is reportable.