[1] Univ Helsinki, HUS Med Imaging Ctr, Radiol, PB 340, Helsinki 00029, Finland
[2] Helsinki Univ Hosp, PB 340, Helsinki 00029, Finland
[3] Univ Helsinki, Head & Neck Surg Otorhinolaryngol, Helsinki, Finland
[4] Helsinki Univ Hosp, Helsinki, Finland
[5] East Tallinn Cent Hosp, Radiol, Tallinn, Estonia
[6] Univ Turku, Otorhinolaryngol, Turku, Finland
[7] Univ Helsinki, Childrens Hosp, Paediat, Helsinki, Finland
[8] Univ Helsinki, Helsinki, Finland