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Dose Assessment and Area Monitoring

This article explores how to assess personal dose and how long this should be assessed for.
© UK Health Security Agency

Provided that all practicable steps to restrict radiation exposure have been taken, as described in week 3 of this course, it is likely that radiation doses received by dental practice staff and other people will be very low. However, to demonstrate this, some monitoring of the situation is required; and this should include:

  • assessment of personal doses
  • controlled area monitoring

Assessment of Personal Doses

What is Required by IRR17?

image with text: Regulation 19(6) of IRR17states: An employer who has designated an area as a controlled area must not permit a person to enter or remain in such area….unless the employer can demonstrate, by personal dose monitoring or other suitable measurements that doses are restricted….

So what do we need to do?

One of the following options would meet the regulatory requirement:

  • issue all staff who enter controlled areas with a personal dosemeter provided by an approved dosimetry service (ADS), which reports the assessed doses to the employer

photo of personal dosemeter

  • issue staff with direct-reading electronic personal dosemeters that are suitable for use with X-rays and keep a log of the recorded doses locally

photo of direct-reading electronic personal dosemeters

  • estimate the annual doses based on measurements made at the operator’s position as part of the arrangements for controlled area monitoring (see below)

How long should this go on for?

The purpose of personal dose assessment is to demonstrate that radiation doses to people entering the controlled area are restricted as far as is reasonably practicable. Based on this, the Dental GNs recommend assessing doses for at least six months in order to get reliable estimates of the likely annual effective doses to these staff. The assessment should be repeated if there are any significant changes to equipment or working practices.

Controlled Area Monitoring

What is required by IRR17?

image with text: Regulation 20(1) of IRR17 states: Every employer who designates an area as a controlled…area must take such steps as are necessary (otherwise than by use of assessed doses of individuals)…to ensure that levels of ionising radiation are adequately monitored for each such area… Regulation 20(5) says: The employer must… make suitable records of the results of the monitoring and… keep the records … for at least 2 years …

So what do we need to do?

One of the following options would meet the regulatory requirement:

  • arrange for the RPA to directly measure the levels of radiation at the operator’s position and other occupied areas outside each controlled area, using suitable equipment
  • measure the levels of radiation at the operator’s position and other occupied areas, using dosemeters that are left in situ for an extended period of time (e.g. three months)
  • arrange for the RPA to calculate the levels of radiation in occupied areas outside the controlled area based on measurements of radiation output from the X-ray set made as part of routine equipment performance tests

How Often Should We Monitor?

The purpose of the area monitoring is to ensure that the controlled area remains correctly designated. In dental radiography, it is unlikely that radiation levels in and around the controlled area will fluctuate significantly, and the risk of significant exposure is low. Based on this low risk, the Dental GNs recommend carrying out these measurements at three-yearly intervals, or if there are any significant changes to equipment or working practices.

Summary

The decision about which methods to use for personal monitoring and controlled area monitoring should be made with your RPA as part of the radiation risk assessment process; this should be reviewed if there are any significant changes to your equipment or working practices.

Records of personal doses should be kept for at least two years after the end of the calendar year to which they relate.

Records of controlled area monitoring, including the location, the method used, the results, the name of the person making the measurement, and the date, should be kept for at least three years.

© UK Health Security Agency
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Dental Radiography: Radiation Protection in Dental Practice

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