Received: 7 August 2018
Accepted: 26 September 2018
First Online: 5 October 2018
Ethics approval and consent to participate
: All procedures in studies involving humans were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The Institutional Review Board of Hokkaido University Hospital is the local ethics committee that reviewed and approved the protocol.
: Not applicable.
: The authors declare that they have no competing interests.
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