Figure 1

Cephalometric landmarks and linear and angular measurements. S, Sella; N, Nasion; A, subspinale; B, supramentale; AH, Anterior Hyoid; Go, Gonion; Me, Menton; C3, Third Vertebra; PNS, posterior nasal spine; U, Tip of the Uvula; ANS, anterior nasal spine; Pm, Pterygomaxillare; Ba, Basion; V, Vallecula. SNA, smaller angle which is formed by sella(S), nasion(N), and A point; ANB, smaller angle which is formed by A point, nasion(N), and B point. AH⊥MP, the perpendicular distance between AH and Go-Me line; AH-C3, the distance between AH and the third vertebra; SPT, maximum width of soft palate which is perpendicular to PNS-U line; PNS-U, the distance between PNS and U; NL/PNS-U, smaller angle between ANS-Pm line and PNS-U line; NAS, nasal airway space, the distance between the intersection of Ba-PNS and posterior pharyngeal wall and PNS; SOAS, superior oral airway space, the distance between the ventral surface of the soft palate and the dorsal surface of the tongue, measured through a point midway between PNS and U, parallel to the line that intersects gonion and menton; MOAS, middle oral airway space, the perpendicular distance between U and posterior pharyngeal wall; IOAS, inferior oral airway space, the distance between the posterior pharyngeal wall and the dorsal surface of the base of the tongue, measured on the line that intersects gonion and menton; HAS, hyoid airway space, the perpendicular distance between V and posterior pharyngeal wall.