Received: 11 September 2020
Accepted: 9 November 2020
First Online: 19 November 2020
Ethics approval and consent to participate
: This study was approved by the Okayama University Ethics Committee (K2010-008).Written informed consent was obtained for all participants.
: Written informed consent was obtained for all participants.
: The authors declare that they have no competing interests. The portable shield for the study was kindly provided by HibiiX Co, Ltd (Mizuho, Japan), without any financial support.