Received: 29 March 2019
Accepted: 18 June 2019
First Online: 26 July 2019
Ethics approval and consent to participate
: The study was approved by the institutional review board of Tokyo Medical and Dental University (Approval number, M2017–351), and the study was conducted in accordance with the ethical standards of the Declaration of Helsinki. The requirement for written informed consent was waived.
: Not applicable.
: The authors declare that they have no competing interests.