Upper Airway Changes following Functional Treatment with the Headgear Herbst or Headgear Twin Block Appliance Assessed on Lateral Cephalograms and Magnetic Resonance Imaging

Figure 3

Landmarks and measurements of the upper airway on MRI. The nasopharynx (NA) was measured on the axial cross-section of the airway passing through the palatal plane. The retropalatal oropharynx (RP) was measured on the axial cross-section of the airway with the minimum area, between the palatal plane and the tip of the uvula. The retroglossal oropharynx (RG) was measured on the axial cross-section of the airway with the minimum area, between the tip of the uvula and the tip of epiglottis. The hypopharnx (HP) was measured on the axial cross-section of the airway passing through the tip of epiglottis.