Text and Data Mining valid from 2017-12-27
Received: 2 July 2017
Accepted: 1 December 2017
First Online: 27 December 2017
Compliance with ethical standards
: There are no potential conflicts of interest for each of the authors.
: The present study protocol was reviewed and approved by the institutional review board of Wonju Severance Christian Hospital (Reg. No. CR316111). Informed consent was exempted, because it was a retrospective study.