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.

Keywords: children; cone beam computed tomography; upper airway; validation.

Figures

Figure 1

Orientation of the CBCT scan. (a) Coronal plane; (b) sagittal plane, Frankfort plane is indicated by the green line; (c) axial plane. Ba, basion; CG, crista galli; Or, orbitale. For colour images please see online.

Figure 2

Upper airway assessment. (a) Margins for delineation of the upper airway. Green lines indicate the margins used to delineate the airway according to Table 2. The yellow point represents the seed point. (b) Margins for minimal cross-sectional area. The red lines indicate the upper and lower limits used to measure the minimal cross-sectional area. For colour images please see online.