2.4 Paranasal sinus computed tomography (CT) imaging
The examination of paranasal sinus CT(Toshiba Aquilion, Tokyo, Japan) was performed in each participant, and CT scoring was according to Lund-Mackay scoring system(15) and the olfactory cleft scoring protocol(16). The L-M CT scoring system contained scoring for the following sinuses: frontal sinus (FS), maxillary sinus (MS), anterior ethmoid sinus (AES), posterior ethmoid sinus (PES), sphenoid sinus (SS) and ostiomeatal complex score (OMC), in which every sinus was assessed with 0 indicating “Normal”, 1 indicating “partly opacification” and 2 indicating “whole opacification”, and OMC was assessed with 0 indicating “Normal” and 2 indicating “whole opacification”. In addition, whole ethmoid sinus (ES) score, ES score/MS score ratio and PES score/AES score ratio were calculated. Similar to the above scoring system, each OC was evaluated by a similar scale of 0 indicating “no opacification”, 1 indicating “partial opacification” and 2 indicating “total opacification”. All of paranasal sinus CT scores were evaluated by two independent radiologists.