Article History
Received: 28 April 2018
Accepted: 3 December 2018
First Online: 20 December 2018
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board at Severance Hospital (approval number: 4–2017-1199). Written consent was not necessary for this study due to its retrospective nature.
: Not applicable.
: The authors declare that they have no competing interests.
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