Establishment of a diagnostic reference level for dental intraoral bitewing X-rays in Western Australia

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Rik Nezich, consultant Medical Physicist at Precision Radiation Services, has co-authored a new research paper in Physical and Engineering Sciences in Medicine, titled “Establishment of a local diagnostic reference level for dental intraoral bitewing X-rays”. This study aimed to measure the distribution of radiation doses that are typically applied by dental X-ray operators in Western Australia when performing a posterior bitewing X-ray on adult patients.

The full paper can be read for free through the publisher’s link: https://rdcu.be/c9aRl.

What is a diagnostic reference level?

A diagnostic reference level (DRL) is defined as the 75th percentile of the distribution of radiation doses applied for a particular imaging procedure throughout a geographical area. Practices should periodically compare their doses to relevant DRLs and make systematic changes to their X-ray equipment usage if a DRL value is consistently exceeded. Prior to this study, no DRLs for dental intraoral radiography had been established in Western Australia or nationally.

Methods

The study involved a survey of 811 intraoral dental X-ray units across Western Australia.

Dental practitioners were asked to describe their typical radiographic technique for performing a posterior bitewing on an adult patient. Where this was not possible, the pre-programmed settings for a bitewing X-ray were selected instead. The incident air kerma (dose in air at the end of the cone), and air-kerma area product (DAP) were then measured using a calibrated radiation dose meter.

Key research findings

  • DRL values of 2.0 mGy incident air kerma and 57 mGy cm2 dose area product (DAP) were established for a posterior bitewing X-ray of an adult patient in Western Australia.
  • This DRL value for incident air kerma is higher than those established in similar studies overseas; such as in the UK (1.2 mGy) and India (1.5 mGy).
  • The majority (93%) of dental X-ray units in WA used photostimulable phosphor (PSP) image receptors. About 6% used direct digital (DDR) sensors, while 1% still used film. Average air kermas were highest for film (2.7 mGy), intermediate for phosphors sensors (1.7 mGy), and lowest for direct digital sensors (1.6 mGy).
  • The three most common X-ray unit models were the Planmeca ProX (n=197), KaVo Focus (n=80), and De Gotzen (Acteon Satelec) X-Mind (n=71). The average dose varied considerably across X-ray unit models. This is most likely due to differences in exposure factors pre-programmed into the units.
  • Uptake of rectangular collimation or long-cone techniques, both effective for reducing radiation dose, was found to be very low in WA. This can be compared to a UK study which found that the majority (67%) of practices used rectangular collimation.
Histogram of incident air kerma for film, DR and PSP image receptors.

    Conclusion

    The establishment of dental intraoral DRLs for Western Australia will provide an opportunity for dental practitioners to use local DRLs to optimise the radiation protection of their patients. Optimisation activities could, for example, involve modifications to exposure settings, adoption of rectangular collimators or long cone techniques, use of of direct digital image receptors, reprogramming of X-ray unit settings, or purchase of ‘lower dose’ X-ray units.

    Precision Radiation Services has qualified Medical Physicists that can assist you with radiation protection. Feel free to ask us about your imaging doses at your next compliance test.

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