X-ray examination dose surveys: how accurate are my results?

  • Stephen Taylor
  • Alain Van Muylem
  • Nigel Howarth
  • Pierre Alain Gevenois
  • Denis TackEmail author



To determine the variabilities of dose-area-products (DAP) of frequent X-ray examinations collected for comparison with diagnostic reference levels (DRLs).


DAP values of chest, abdomen, and lumbar spine examinations obtained on devices from two manufacturers were collected in three centers over 1 to 2 years. The variability of the average DAP results defined as the 95% confidence interval in percentage of their median value was calculated for increasing sample sizes, each examination and center. We computed the sample sizes yielding variabilities lower or equal to 25% and 10%. The effect of narrowing patient selection based on body weight was also investigated (ranges of 67–73 Kg, or 60–80 Kg).


DAP variabilities ranged from 75 to 170% of the median value when collecting small samples (10 to 20 DAP). To reduce this variability, larger samples are needed, collected over up to 2 years, regardless of the examination and center. A variability  10% could only be reached for chest X-rays, requiring up to 800 data. For the abdomen and lumbar spine, the lowest achievable variability was 25%, regardless of the body weight selection, requiring up to 400 data.


Variabilities in DAP collected through small samples of ten data as recommended by authorities are very high, but can be reduced down to 25% (abdomen and lumbar spine) or even 10% (chest) through a substantial increase in sample sizes. Our findings could assist radiologists and regulatory authorities in estimating the reliability of the data obtained when performing X-ray dose surveys.

Key Points

• Low but reasonable variabilities cannot be reached with samples sized as recommended by regulatory authorities. Higher numbers of DAP values are required to reduce the variability.

• Variabilities of 10% for the chest and 25% for abdomen and lumbar spine examinations are achievable, provided large samples of data are collected over 1 year.

• Our results could help radiologists and authorities interpret X-rays dose surveys.


Radiation protection Radiography Surveys and questionnaires 



Automatic exposure control


Volume computed tomographic dose index


Dose area product


Diagnostic reference level


Entrance surface dose


European Union





The authors state that this work has not received any funding.

Compliance with ethical standards


The scientific guarantor of this publication is Denis Tack.

Conflict of interest

The authors of this manuscript declare no relationships with any companies whose products or services may be related to the subject matter of the article.

Statistics and biometry

One of the authors has significant statistical expertise.

Informed consent

Written informed consent was waived by the Institutional Review Board.

Ethical approval

Institutional Review Board approval was obtained.


• retrospective

• observational

• multicenter study


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Copyright information

© European Society of Radiology 2019

Authors and Affiliations

  1. 1.Department of RadiologyHôpital Ambroise ParéMonsBelgium
  2. 2.Department of PneumologyHôpital ErasmeBrusselsBelgium
  3. 3.Department of RadiologyClinique des GrangettesGenevaSwitzerland
  4. 4.Department of RadiologyHôpital ErasmeBrusselsBelgium
  5. 5.Department of Radiology, EPICURAClinique Louis CatyBaudourBelgium

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