title: The Potential Role of Subglottal Convergence Angle and Measurement.
abstract: OBJECTIVE
  This study aimed to explore subglottal convergence angle measurement. We hypothesize that the angle will change with glottis closure condition. Changes to the angle may alter vocal fold stress distribution, which could result in vocal fold pathologies.
  
  
  METHODS
  Three vocal fold positions were evaluated by the degree of glottal closure and divided into three groups. Neck computed tomographic images of the subjects were gathered, and three-dimensional (3D) models of the vocal folds and the airway were reconstructed using Mimics software, through which the subglottal convergence angle was measured. Using one-way factor analysis of variance, we compared the angle among three groups. We explored the effect of the angle on vibration based on the material oblique section stress analysis.
  
  
  RESULTS
  The subglottal convergence angle was effectively measured from 3D models. The angle changed with degree of glottal closure, with statistically significant differences among the three groups (P < 0.01). Changes to the angle alter subglottal stress distribution in the subglottal shear or normal direction by the material oblique section stress analysis theory. Larger subglottal convergence angle might reduce subglottal pressure in the shear direction below the vocal folds, which would make vibration and vocal fold mucosal wave generation more difficult.
  
  
  CONCLUSIONS
  3D model generation from computed tomographic data is an effective method of measuring the subglottal convergence angle, which changes with the degree of glottis closure, and may affect subglottal pressure distribution in the subglottal shear or normal direction and influence vocal fold vibration.
authors.affiliation: ENT Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China.
authors.forename: Xinlin
authors.initials: X
authors.lastname: Xu
authors.affiliation: Radiology Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China.
authors.forename: Jingan
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Erin E
authors.initials: EE
authors.lastname: Devine
authors.affiliation: Radiology Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Radiology Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Zhong
authors.affiliation: Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin.
authors.forename: Maxwell R
authors.initials: MR
authors.lastname: Courtright
authors.affiliation: ENT Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China.
authors.forename: Li
authors.initials: L
authors.lastname: Zhou
authors.affiliation: ENT Department, Xiamen University Zhongshan Hospital, Xiamen, Fujian, China. Electronic address: peiyun_zhuang@yahoo.com.
authors.forename: PeiYun
authors.initials: P
authors.lastname: Zhuang
authors.affiliation: Department of Surgery, Division of Otolaryngology-Head and Neck Surgery, University of Wisconsin-Madison School of Medicine and Public Health, Madison, Wisconsin; ENT Department, Fudan University Shanghai EENT Hospital, Shanghai, China.
authors.forename: Jack J
authors.initials: JJ
authors.lastname: Jiang
mesh_terms: D000328:Adult; D001696:Biomechanical Phenomena; D016022:Case-Control Studies; D005260:Female; D005931:Glottis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D008953:Models, Anatomic; D066230:Patient-Specific Modeling; D010699:Phonation; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D012984:Software; D013314:Stress, Mechanical; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014732:Vibration; D014826:Vocal Cord Paralysis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014827:Vocal Cords / Q000000981:diagnostic imaging* / Q000503:physiopathology; D014833:Voice Quality
keywords: 3D model; incomplete glottal closure; oblique section; subglottal convergence angle; vocal fold