Amira 3d visualization and modeling system

AMIRA 3D visualization and modeling system (Visage Imaging, Carlsbad, USA) was used to calculate the volume of right and left OB using the planimetric manual contouring (PMC) technique (surface in mm²) (Fig 1A and 1C). The OB sequence included acquisition of 1 mm thick T2- weighted fast spin images, in the coronal plane that covers middle and anterior portions of the skull base. A standardized PMC protocol was applied to all scans [22 (link)]. Firstly, number of slices with clear visibility of the OB were selected. On each successive slice of brain, contours on left and right side of OB were manually drawn. The proximal end of the OB was defined by the abrupt change in the diameter at the beginning of the olfactory tract [22 (link), 23 (link)].Two trained observers blind to the diagnosis and clinical characteristics of the subjects, calculated the volumes (in mm³).

Data was analyzed using SPSS 21 for Windows (SPSS Inc., Chicago, IL, USA). AMIRA 3D visualization and modeling system (Visage Imaging, Carlsbad, CA, USA) was used to calculate OB volumes.

The volumetric measurements of the right and left OB were performed by manual segmentation of the coronal slices through the OBs using the AMIRA 3D visualization and modeling system (Visage Imaging, Carlsbad, USA). As first shown by Yousem and colleagues [14 (link)] this procedure is highly reliable being able to obtain coefficients of correlation for repeated measurements by a single observer greater than .92 while for measurements across observers the coefficients were event greater (.96). The segmentation on the T2-weighted MRI of the 14 subjects acquired in Brescia was done by one observer twice and in a blind way in respect to the set of the geographical location of origin, and therefore to the exposure classification of each subject. The measure of the OB for each subject was then evaluated by the average of the two.
Further statistical analyses were carried out by means of SPSS 19.0 (SPSS Inc., Chicago, IL, USA). To test the hypothesis we used the Mann-Whitney U test with the level of significance set at 0.05.