Received: 15 July 2019
Accepted: 21 November 2019
First Online: 2 December 2019
Ethics approval and consent to participate
: This study was performed in accordance with the ethical standards detailed in the Declaration of Helsinki. The study was reviewed and approved by the Hokkaido University Hospital Review Board 017–0153.Written informed consent from all participate was obtained.
: Not applicable.
: The authors declare that they have no competing interests.