Text and Data Mining valid from 2019-03-19
Received: 17 December 2018
Accepted: 8 March 2019
First Online: 19 March 2019
Ethics approval and consent to participate
: The study was approved by the Institutional Review Board of Gunma University Hospital. The board waived the need for informed consent, as this was a retrospective study.
: Not applicable.
: The authors declare that they have no competing interests.
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