1. Center for Machine Vision and Signal Analysis, University of Oulu, Oulu, Finland
2. Medical Research Center Oulu, Oulu University Hospital and University of Oulu, Oulu, Finland
3. Department of Otorhinolaryngology, Oulu University Hospital, Oulu, Finland
4. Research Unit of Otorhinolaryngology and Ophthalmology, University of Oulu, Oulu, Finland