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. 2016 Jul 29;11:98. doi: 10.1186/s13014-016-0677-8

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© The Author(s). 2016

Open AccessThis article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

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Fig. 3 — Different slices of the Catphan’s modules used for image quality evaluation. a A bar pattern module of increasing spatial frequency (lp/cm), used for determining spatial resolution of the protocols. b A low contrast module used in calculating CNR of the various protocols. c A homogeneous module used in determining uniformity, with four ROI (anterior, posterior, right, and left) equidistant from a centrally located ROI. d A sensitometry module containing materials of known electron density, used in the calculating HU difference from baseline