Text and Data Mining valid from 2019-04-05
Received: 28 May 2018
Accepted: 28 March 2019
First Online: 5 April 2019
Ethics approval and consent to participate
: This study was approved by the Ethics committee of Tohoku University Graduate School of Medicine (Approval No: 2016–1-747). The requirement of informed consent was waived and an opt-out method was used due to the retrospective design of the study.
: The authors declare that they have no competing interests.
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