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


CONCLUSIONS
• 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.
Department of Radiology, Faculty of Dentistry, Chulalongkorn University, 34 Henri-Dunant Rd, Patumwan, 10330, Bangkok, Thailand. ruben.pauwels@med.kuleuven.be.|OMFS-IMPATH Research Group, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium. ruben.pauwels@med.kuleuven.be.
Ruben
R
Pauwels
OMFS-IMPATH Research Group, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
Reinhilde
R
Jacobs
Laboratory of Experimental Radiotherapy, Department of Oncology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
Ria
R
Bogaerts
Medical Physics & Quality Assessment, Department of Imaging and Pathology, Biomedical Sciences Group, University of Leuven, Leuven, Belgium.
Hilde
H
Bosmans
Department of Radiology, Faculty of Dentistry, Chulalongkorn University, 34 Henri-Dunant Rd, Patumwan, 10330, Bangkok, Thailand.
Soontra
S
Panmekiate
D000328:Adult; D002648:Child; D054893:Cone-Beam Computed Tomography / Q000379:methods*; D005260:Female; D006257:Head / Q000000981:diagnostic imaging; D006801:Humans; D008297:Male; D019047:Phantoms, Imaging; D011829:Radiation Dosage; D011861:Radiography, Dental / Q000379:methods*
Cone-beam computed tomography; Dentistry; Noise; Paediatrics; Radiation protection