Received: 3 January 2019
Accepted: 28 April 2019
First Online: 10 May 2019
Ethics approval and consent to participate
: Our study was carried out according to the ethical guidelines of the Declaration of Helsinki. It was approved by the institutional review board of Oita University Hospital, which determined that our retrospective study did not require additional informed consent. We removed any details that might disclose the identities of the subjects.
: Not applicable.
: The authors declare that they have no competing interests.
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