Text and Data Mining valid from 2018-12-21
First Online: 21 December 2018
Compliance with ethical guidelines
: F. Chen, T. Shi, Y. Li, H. Wang, F. Luo and T. Hou declare that they have no competing interests.
: This article does not contain any studies with human participants or animals performed by any of the authors. For images or other information within the manuscript which could identify patients, informed consent was obtained from them and/or the legal guardians.