2.2. Radiologic Evaluations and Calculations
HRCT examinations had been performed with multidetector CT system (Activision 16-row CT scanner; Toshiba Medical Systems, Otawara, Japan) at 120–400 mA and 80–160 kV, and CT slides 0.5 mm in thickness; a matrix size 512 × 512 were obtained, and approximately 120–300 images per CT were evaluated.
Mastoid pneumatization was evaluated by using the criteria Diamant12, Doland 13, and Valvassori et al.14 described: fully pneumatized, diploic (partial pneumatized), or sclerotic (non-pneumatized) (Figure 1) . Petrous apex and perilabyrinthine pneumatization were evaluated as present or absent.
Paranasal sinus volumes were calculated by using the formula defined by Barghouth et al. in 2002 15. The greatest depth, width and length of the sinuses were calculated respectively by using axial and coronal sections, and the Sinus volume index (SVI) was found by the equation: SVI = ½. A × B × C (Figure 2) . Due to the complex anatomy and vague borders of the sinuses, ethmoid sinus volumes were not calculated.
Two otolaryngologists blindly evaluated all CT scans. The mean values of the measurements obtained by the two physicians were used for analyses of the sinus volumes. For the evaluation of mastoid, petrous apex, and perilabyrinthine cell pneumatization , the results of the two otolaryngologists were compared, if any conflict was present, the CT scan was further evaluated by an associated professor (B.P).