Text and Data Mining valid from 2019-01-23
Received: 16 July 2018
Accepted: 17 January 2019
First Online: 23 January 2019
Ethics approval and consent to participate
: The study was approved by the institutional review board of the Tsuchiura Kyodo General Hospital (approval Nos. 534 and 623). All patients and their parents provided informed consent.
: Not applicable.
: The authors declare that they have no competing interests.
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