Text and Data Mining valid from 2018-08-20
Received: 9 April 2018
Accepted: 5 June 2018
First Online: 20 August 2018
Ethics approval and consent to participate
: All procedures in this study were approved by the Ethics Committee of Tokyo Medical and Dental University (No. 419) and complied with the Code of Ethics of the World Medical Association (Declaration of Helsinki).
: Not applicable
: The authors declare that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.