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Article History

Received: 24 February 2017

Revised: 18 April 2017

Accepted: 4 May 2017

First Online: 7 June 2017

Compliance with ethical standards

:

: The scientific guarantor of this publication is Gi Jeong Cheon.

: 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.

: This work was not supported by any fund.

: No complex statistical methods were necessary for this paper.

: Institutional Review Board approval was obtained.

: Written informed consent was waived by the Institutional Review Board.

: • retrospective• diagnostic or prognostic study• performed at one institution