Text and Data Mining valid from 2018-10-29
Received: 16 March 2018
Accepted: 17 October 2018
First Online: 29 October 2018
Compliance with ethical guidelines
: K. Burjakow, R. Fietkau, F. Putz, N. Achterberg, S. Lettmaier, and S. Knippen declare that they have no competing interests.
: All procedures performed were in accordance with the ethical standards of the institutional research committee and with the 1964 Helsinki declaration and its later amendments. For this retrospective study, formal consent is not required.