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. 2016;89(1057):20150346.
doi: 10.1259/bjr.20150346. Epub 2015 Nov 6.

Updated estimates of typical effective doses for common CT examinations in the UK following the 2011 national review

Paul C Shrimpton  1 , Jan T M Jansen  1 , John D Harrison  1
Affiliations

Updated estimates of typical effective doses for common CT examinations in the UK following the 2011 national review

Paul C Shrimpton et al. Br J Radiol. 2016.

Abstract

Objective: To investigate the impact of evolving International Commission on Radiological Protection (ICRP) recommendations concerning calculation of effective dose (E) and compare updated typical UK values for common CT examinations with previous data.

Methods: Monte Carlo simulations have provided normalized organ doses relating to 15 CT scanner models and 5 virtual reference adults. Series of representative E/dose-length product (DLP) coefficients were derived for common examinations on the separate bases of not only older stylized mathematical phantoms and voxel phantoms presently recommended by ICRP, but also the 1977, 1990 and 2007 formulations for E. Updated E/DLP coefficients were applied to typical values of DLP from the 2011 UK survey.

Results: Changes in ICRP recommendations that have arisen from improving evidence on stochastic risk, influence values of E by up to a factor two for CT examinations of the head and neck, although differences for the trunk typically amount to ±10%. Adoption of the voxel rather than the mathematical phantoms used previously can lead to further changes in E by a few tens of percent. Updated typical values of E for UK CT examinations range from 2 to 20 mSv. Increases by 20-400% since 2003 arise not only from increases by 30-160% in typical values of DLP, but also increases by 30-90% in relation to E/DLP coefficients for examinations of the trunk.

Conclusion: Values of E, including updated typical data for UK CT, should be compared with caution in relation to their purpose and underlying factors concerning their calculation.

Advances in knowledge: Updated E/DLP coefficients and typical values of E for UK CT, and an appreciation of factors influencing these data.

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Figures

Figure 1.
Figure 1.
Variation in E103/DLP for simulated contiguous irradiation of 1 cm slabs of the HPA18+, AM and AF phantoms by a Siemens Definition scanner operating at 120 kV. Note that E103 is defined by ICRP in relation to a male/female average. AF, adult female; AM, adult male; DLP, dose-length product; E, effective dose; ICRP, International Commission on Radiological Protection.
See this image and copyright information in PMC

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