Evaluation of the correlation between different boundaries used in upper airway assessment

Introduction: The aim of this study was to evaluate the correlation of the volume and minimum axial area (MAA) measurements between different upper and lower boundaries used in oropharyngeal airway assessment. Materials and Method: Cone Beam Computed Tomography (CBCT) scans of 49 subjects taken for pre-orthognathic surgery planning were obtained retrospectively from the archive of the Hacettepe University Department of Orthodontics (n=49; 32 females, 17 males; mean age= 20.9 ± 5.22). Volume and MAA of oropharngeal airway were measured in 32 different airway segmentations created with 4 different upper (palatal plane, horizontal plane passing through the PNS point, PNS-Ba plane, the plane passing through the PNS point and the lower medial border of the first cervical vertebrae) and 8 different lower boundaries (the horizontal planes passing through the most anteroinferior point of the second, third and fourth cervical vertebrae, tip of the epiglottis, and vallecula, the plane between the most anteroinferior point of the fourth cervical vertebrae and the corner of hyoid bone, the plane between the most anteroinferior point of the third cervical vertebrae and menton, the plane between the most anterosuperior point of the fourth cervical vertebrae and menton) using the Dolphin3D (Dolphin Imaging & Management Solutions, Chatsworth, California, ABD) software. All measurements were performed by the same examiner and were repeated 2 weeks apart. Results: Volume and MAA showed excellent intraobserver reliability (0.997 and 0.999 intraclass correlation coefficients, respectively) and a high level of positive correlation (r= 0.896-0.999, and r=0.859-1.00, respectively). Conclusion: All measurements between the lower and upper boundaries showed a high correlation. It was found that the lower and upper limits that assessed in this study can be used safely in future upper airway studies according to the need of studies.