title: Quantitative upper airway imaging with anatomic optical coherence tomography.
abstract: BACKGROUND
  Measurements of upper airway size and shape are important in investigating the pathophysiology of obstructive sleep apnea (OSA) and in devising, applying, and determining the effectiveness of treatment modalities. We describe an endoscopic optical technique (anatomic optical coherence tomography, aOCT) that provides quantitative real-time imaging of the internal anatomy of the human upper airway.
  
  
  METHODS
  Validation studies were performed by comparing aOCT- and computed tomography (CT)-derived measurements of cross-sectional area (CSA) in (1) conduits in a wax phantom and (2) the velo-, oro-, and hypopharynx during wakefulness in five volunteers. aOCT scanning was performed during sleep in one subject with OSA.
  
  
  RESULTS
  aOCT generated images of pharyngeal shape and measurements of CSA and internal dimensions that were comparable to radiographic CT images. The mean difference between aOCT- and CT-derived measurements of CSA in (1) the wax phantom was 2.1 mm(2) with limits of agreement (2 SD) from -13.2 to 17.4 mm(2) and intraclass correlation coefficient of 0.99 (p < 0.001) and (2) the pharyngeal airway was 14.1 mm(2) with limits of agreement from -43.7 to 57.8 mm(2) and intraclass correlation coefficient of 0.89 (p < 0.001). aOCT generated quantitative images of changes in upper airway size and shape before, during, and after an apneic event in an individual with OSA.
  
  
  CONCLUSIONS
  aOCT generates quantitative, real-time measurements of upper airway size and shape with minimal invasiveness, allowing study over lengthy periods during both sleep and wakefulness. These features should make it useful for study of upper airway behavior to investigate OSA pathophysiology and aid clinical management.
authors.affiliation: Optical+Biomedical Engineering Laboratory, School of Electrical, Electronic, and Computer Engineering, University of Western Australia, 35 Stirling Highway, Crawley, Western Australia 6009. julian-a@ee.uwa.edu.au
authors.forename: Julian J
authors.initials: JJ
authors.lastname: Armstrong
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Leigh
authors.forename: David D
authors.initials: DD
authors.lastname: Sampson
authors.forename: Jennifer H
authors.initials: JH
authors.lastname: Walsh
authors.forename: David R
authors.initials: DR
authors.lastname: Hillman
authors.forename: Peter R
authors.initials: PR
authors.lastname: Eastwood
mesh_terms: D000328:Adult; D004724:Endoscopy / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D066298:In Vitro Techniques; D008297:Male; D015588:Observer Variation; D019047:Phantoms, Imaging; D012016:Reference Values; D015203:Reproducibility of Results; D012137:Respiratory System / Q000033:anatomy & histology / Q000000981:diagnostic imaging*; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000503:physiopathology; D041623:Tomography, Optical Coherence / Q000295:instrumentation* / Q000379:methods; D014057:Tomography, X-Ray Computed / Q000379:methods