[1] Department of Otorhinolaryngology,
[2] University of Essen,undefined
[3] Hufelandstrasse 55,undefined
[4] 45122 Essen,undefined
[5] Germany Tel.: +49-201-7232481; Fax: +49-201-7235903 e-mail: markus.fischer@uni-essen.de,undefined
[6] Department of Radiotherapy,undefined
[7] University of Essen,undefined
[8] Essen,undefined
[9] Germany,undefined
[10] Department of Radiotherapy,undefined
[11] Charité,undefined
[12] Humboldt University,undefined
[13] Berlin,undefined
[14] Germany,undefined