Important queries for the airway analysis in cone-beam computed tomography scans : threshold tool and voxel size protocol

Context: There is an expansion of the use of cone-beam computed tomography (CBCT) for maxillofacial diagnosis. However, some researchers have demonstrated inconsistencies between the results of airway analysis tools. Aim: This study aims to analyze the threshold tool presented in postprocessing software for airway volume estimation and the influence of voxel size in these measurements. Methods: Three hundred and sixteen-selected CBCT scans (0.2, 0.25, and 0.4 voxel sizes) were retrospectively analyzed. A trained and calibrated examiner performed the volume measurements in specific sites in upper airway at 25 and chosen threshold tool using the Dolphin Software. Statistical Analysis Used: Analysis of variance (ANOVA) was used to compare the thresholds for each voxel and the differences between the preset and the chosen thresholds, while paired t -test to compare differences between the chosen thresholds for voxel size groups. Results: The threshold values range from 26 to 43. The mean of the threshold selected for voxel 0.4 was significantly lower than the mean thresholds of 0.2 mm to 0.25 mm voxel. Small volumes were obtained with the preset threshold tool for all voxel sizes when compared with the chosen threshold. The mean of differences in volumes between preset and chosen threshold decreased with the increase of voxel size. Conclusion: The voxel size protocol influenced the threshold value choice for volume measurements in upper airway analysis. The thresholds near to 30 seem better filling the airway space.