Received: 4 January 2020
Accepted: 15 June 2020
First Online: 24 June 2020
Ethics approval and consent to participate
: This study was approved by the Institutional Review Board of Affiliated Hospital of Chengde Medical University. Written informed consent was obtained from all patients. No children (under 16 years old) were included in this study.
: Not applicable.
: All authors declare that they have no competing interests.