1. Department of Technical Physics, University of Eastern Finland, Kuopio, Finland
2. Department of Technical Physics, University of Eastern Finland and Science Service Center, Kuopio University Hospital, Kuopio, Finland
3. Diagnostic Imaging Center, Kuopio University Hospital, Kuopio, Finland
4. Reykjavik University Sleep Institute, School of Technology, Reykjavik University, Reykjavik, Iceland
5. Landspitali–The National University Hospital of Iceland, Reykjavik, Iceland