Received: 2 April 2020
Accepted: 23 December 2020
First Online: 8 January 2021
Ethics approval and consent to participate
: This study was approved by the Hokkaido University Institutional Review Board (#015–0096), and written informed consent for participation in the study was obtained from all participants.
: All subjects participating in the image acquisition signed the consent form.
: The authors declare that they have no competing interests.