European Radiology

, Volume 27, Issue 1, pp 279–285 | Cite as

Determination of size-specific exposure settings in dental cone-beam CT

  • Ruben PauwelsEmail author
  • Reinhilde Jacobs
  • Ria Bogaerts
  • Hilde Bosmans
  • Soontra Panmekiate



To estimate the possible reduction of tube output as a function of head size in dental cone-beam computed tomography (CBCT).


A 16 cm PMMA phantom, containing a central and six peripheral columns filled with PMMA, was used to represent an average adult male head. The phantom was scanned using CBCT, with 0-6 peripheral columns having been removed in order to simulate varying head sizes. For five kV settings (70-90 kV), the mAs required to reach a predetermined image noise level was determined, and corresponding radiation doses were derived. Results were expressed as a function of head size, age, and gender, based on growth reference charts.


The use of 90 kV consistently resulted in the largest relative dose reduction. A potential mAs reduction ranging from 7 % to 50 % was seen for the different simulated head sizes, showing an exponential relation between head size and mAs. An optimized exposure protocol based on head circumference or age/gender is proposed.


A considerable dose reduction, through reduction of the mAs rather than the kV, is possible for small-sized patients in CBCT, including children and females. Size-specific exposure protocols should be clinically implemented.

Key Points

Fixed exposure settings in CBCT results in overexposure for smaller patients

For children, considerable dose reduction is possible without compromising image quality

A reduction in mAs is more dose-efficient than a kV reduction

An optimized exposure protocol was proposed based on phantom measurements

This protocol should be validated in a clinical setting


Cone-beam computed tomography Dentistry Paediatrics Radiation protection Noise 



The scientific guarantor of this publication is Dr. Ruben Pauwels. 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. This study has received funding by Chulalongkorn University.

No complex statistical methods were necessary for this paper. Institutional Review Board approval was not required because this was a phantom study. Methodology: experimental, multicenter study.

Supplementary material

330_2016_4353_MOESM1_ESM.pdf (633 kb)
ESM 1 (PDF 633 kb)
330_2016_4353_Fig7_ESM.gif (8 kb)
Figure A1

Attenuation of a 50 keV X-ray beam passing through polymethyl methacrylate (PMMA), as a function of PMMA thickness. Data based on NIST tables [1]. (GIF 7 kb)

330_2016_4353_MOESM2_ESM.tif (930 kb)
High resolution image (TIF 930 kb)
330_2016_4353_Fig8_ESM.gif (9 kb)
Figure A2

Relative mAs required to achieve a constant detector signal as a function of PMMA thickness, relative to 160 mm. Data based on NIST tables [1]. (GIF 8 kb)

330_2016_4353_MOESM3_ESM.tif (979 kb)
High resolution image (TIF 978 kb)


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Copyright information

© European Society of Radiology 2016

Authors and Affiliations

  • Ruben Pauwels
    • 1
    • 2
    Email author
  • Reinhilde Jacobs
    • 2
  • Ria Bogaerts
    • 3
  • Hilde Bosmans
    • 4
  • Soontra Panmekiate
    • 1
  1. 1.Department of Radiology, Faculty of DentistryChulalongkorn UniversityPatumwanThailand
  2. 2.OMFS-IMPATH Research Group, Department of Imaging and Pathology, Biomedical Sciences GroupUniversity of LeuvenLeuvenBelgium
  3. 3.Laboratory of Experimental Radiotherapy, Department of Oncology, Biomedical Sciences GroupUniversity of LeuvenLeuvenBelgium
  4. 4.Medical Physics & Quality Assessment, Department of Imaging and Pathology, Biomedical Sciences GroupUniversity of LeuvenLeuvenBelgium

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