Article History
Received: 24 July 2018
Accepted: 17 December 2018
First Online: 2 January 2019
Compliance with Ethical Standards
: This study was approved by the Institutional Review Board of Kyungpook National University (IRB 2014-0053) and was conducted according to the Helsinki declaration; all subjects were explained in detail the purpose and contents of the study, and each signed an informed consent form.
: The authors declare that there is no conflict of interest.