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Eur Radiol. 2017 Jan;27(1):279-285. Epub 2016 Apr 23.

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

Author information

1
Department of Radiology, Faculty of Dentistry, Chulalongkorn University, 34 Henri-Dunant Rd, Patumwan, 10330, Bangkok, Thailand. ruben.pauwels@med.kuleuven.be.
2
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium. ruben.pauwels@med.kuleuven.be.
3
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
4
Laboratory of Experimental Radiotherapy, Department of Oncology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
5
Medical Physics & Quality Assessment, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
6
Department of Radiology, Faculty of Dentistry, Chulalongkorn University, 34 Henri-Dunant Rd, Patumwan, 10330, Bangkok, Thailand.

Abstract

OBJECTIVES:

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

METHODS:

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.

RESULTS:

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.

CONCLUSIONS:

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.

KEYWORDS:

Cone-beam computed tomography; Dentistry; Noise; Paediatrics; Radiation protection

PMID:
27108296
DOI:
10.1007/s00330-016-4353-z
[Indexed for MEDLINE]

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