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. 2021 Sep 9;10(5):194–203. doi: 10.5492/wjccm.v10.i5.194

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©The Author(s) 2021. Published by Baishideng Publishing Group Inc. All rights reserved.

This article is an open-access article that was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution NonCommercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/Licenses/by-nc/4.0/

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Different protocols. Dotted arrows correspond to ultrasound scans separated by 2 cm intervals. Yellow segments instead represent doppler points. CDUS: Complete doppler ultrasound; ECUS: Extended compression ultrasound; 2-region: Two-region ultrasound.