Proposal of new upper airway margins in children assessed by CBCT

Abstract

Objectives: Recently, studies have performed three-dimensional analyses of upper airways in children. However, there was a lack of airway delineation according to anatomical boundaries and/or easily mobile soft-tissue landmarks were used. The aim of the present study was to define new upper airway margins in children on CBCT according to anatomical bony landmarks and to validate the method. Methods: 25 scans were randomly selected from a larger database containing CBCT scans of children prior to orthodontic treatment (14 girls and 11 boys; mean age, 10.9 ± 2.5 years). Scans were evaluated by two observers. Specific head positioning and virtual orientation protocols were adopted and greyscale thresholding was established for each patient. Volume and minimum cross-sectional area of the oropharynx were calculated. Intra-and interobserver reliability were assessed by reassessment of the CBCTs 2 weeks later. Results: The new airway margins were defined superiorly by a line passing through the palatal plane (anterior nasal spine to posterior nasal spine) extending to the posterior wall of the pharynx, inferiorly by a line passing from the anterosuperior edge of C4 to menton, anteriorly by a line passing from the soft palate to menton, posteriorly and laterally by the respective pharyngeal walls. Method error for airway volume and minimal cross-sectional area was #2.00%, and intra-and interobserver reliability ranged from 0.99 to 1.00. Conclusions: The proposed protocol utilizes easily identifiable bony landmarks to delineate the upper airway on cone beam scans of children and was found to be reliable and reproducible.

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

“…A threshold tool is available so that the examiner can change the airway space-filling degree according to visual inspection. Since there is no standard protocol for these instruments and measurements, [8,14,[20][21][22] the calibrated observer calculated with the preset (25) and the best value that visually could fill the airway borders.…”

Computational fluid dynamics simulation of the upper airway response to large incisor retraction in adult class I bimaxillary protrusion patients

“…Subsequently, the dataset was exported in DICOM (Digital Imaging and Communications in Medicine) file format, and then was read into MIMICS16.0 (Materialism’s Interactive Medical Image Control System) software. After that, the models were reorientated in three planes: in the coronal view, the most inferior points on the infraorbital margin (orbitale) lie on the same horizontal plane; in the sagittal view, the models were reorientated to make the Frankfort plane horizontal; in the axial view, the models were reorientated to make the line through the crista galli and the midpoint on the anterior margin of foramen magnum (basion) vertical16. The upper airway of interest was segmented by setting the threshold between −1024 Hounsfield Units (HU) and −480 HU, and the 3D anatomically accurate patient-specific models were reconstructed.…”

“…Two planes: a line passing from anterior nasal spine to posterior nasal spine and a line passing from the anterosuperior edge of the fourth cervical vertebra (C4) to menton, which have been proved to be reliable and reproducible landmarks for defining upper airway margins16 were uesd to divided the whole pharynx into three parts (nasopharynx, oropharynx, and hypopharynx). In this study, volumes of the whole pharynx (V) and each part of the pharynx: nasopharynx (V na ), oropharynx (V or ), and hypopharynx (V hy ) was calculated.…”

Effects of rapid maxillary expansion on upper airway volume: A three-dimensional cone-beam computed tomography study

“…The Digital Imaging and Communications in Medicine (DICOM) data were processed using Dolphin Imaging Software (version 11.5; Dolphin Imaging and Management Solutions, Chatsworth, Calif). Images were analyzed under the same lighting conditions and by the same investigator using a previously validated protocol, 18 which is briefly outlined below and illustrated in Figure 1.…”

“…17 Anandarajah 18 proposed and validated a standardized method of upper airway assessment using CBCT and has used this technique to demonstrate an association between maxillary and mandibular width and airway volume in healthy untreated children. 19 The aims of this study were (1) to compare changes in pharyngeal airway volume and minimal crosssectional area (MCA) in an RME group with that of a control group matched in age, skeletal age, gender, and mandibular inclination using a validated method of airway volume measurement 18 and (2) to identify pretreatment markers for predicting airway change in the two groups combined.…”