Article History
Received: 26 February 2019
Revised: 31 May 2019
Accepted: 4 June 2019
First Online: 18 June 2019
Compliance with ethical standards
: This study was approved by the ethics committee of Keio University School of Medicine (approval number: 20130506). The requirement for informed consent from the patients was waived according to the regulation in Japan.
: None.