Text and Data Mining valid from 2019-07-23
Received: 5 October 2018
Revised: 13 May 2019
Accepted: 26 June 2019
First Online: 23 July 2019
Compliance with ethical standards
: The scientific guarantor of this publication is Ie Ryung Yoo.
: The authors of this manuscript declare no relationships with any companies, whose products or services may be related to the subject matter of the article.
: No complex statistical methods were necessary for this paper.
: Written informed consent was waived by the Institutional Review Board.
: Institutional Review Board approval was obtained.
: • retrospective• observational• performed at one institution