Text and Data Mining valid from 2019-10-30
Received: 17 July 2019
Accepted: 24 September 2019
First Online: 30 October 2019
Ethics approval and consent to participate
: This study was approved by the Ethics Committee and Institutional Review Board of Keio University Hospital (IRB No. 20080054). A written informed consent was collected from each male volunteer.
: The authors declare that they have no competing interests.